Fitbit Flex review: A most versatile, feature-packed tracker

The $99.95 Fitbit Flex is the newest personal fitness tracker in the company’s lineup. While the Flex isn’t without some flaws, the gadget is the most complete product of its kind you can buy. It can track steps taken, sleep quality, and it syncs data wirelessly with PCs and Macs automatically. Comfortable to wear, the Flex can communicate directly with iPhones and select Android smartphones, and is water-resistant as well. Going head-to-head with other wristband-style exercise products such as the Nike FuelBand  and Jawbone Up , the Flex offers more features and convenience at a lower price than those more expensive devices.

Fitbit Flex Wireless Activity + Sleep Wristband, Black


Make fitness a lifestyle with Fitbit Flex

Made by: Fitbit, Available: In stock


When I first picked up the new Fitbit Flex, I initially considered its unadorned surface and clean, ring shape spartan. After all, the device lacks a real screen capable of displaying alphanumeric characters. Instead the Flex sports a thin sliver of a display cut from smoky dark plastic. Underneath the plastic sits a row of five tiny, white LEDs that blink to indicate the Flex’s status.

The Flex’s flexible rubbery band, however, masks the product’s true complexity. Inside a small pouch on the strap’s underbelly you’ll find the real brains of the operation, a smooth plastic pebble that contains all the Flex’s electronics. In fact, the LEDs visible from the band’s surface are actually located on this little gizmo. Indeed, half the size of the current Fitbit One and Fitbit Zip, the new Flex is Fitbit’s smallest tracker yet.

Other than its LEDs and a Fitbit logo, the only other features you’ll find on the tracker is a line of metal contacts. These are used for charging the Flex’s rechargeable battery through the supplied USB cable and socket adapter.

Popping the Flex into its band is easy, and the tracker even has an arrow indicating which direction it should be inserted. Attaching the band to my wrist is another situation altogether. The Flex has nine oval holes on one side of its wrist strap, and two hard pegs on the other.To button up the band you snap these pegs into the Flex’s notch-shaped holes. In my experience it’s a tricky process that requires a lot of force. Call me a wimp, but I even injured myself attaching the band; I mashed my thumb too hard against my wrist. Fitbit says that it’s aware of this issue and that it should only affect preproduction units such as mine. One benefit of the Flex’s tight wrist lock is that it’s unlikely to become unhooked.

If you spend a lot of time around water or in the rain, the Flex has your back. The device is fully water-resistant and is designed to shrug off exposure to splashes and short immersions in liquid. As a result I was able to both shower and wash dishes with the Flex strapped to my wrist daily. It’s a good thing, too; the Flex is so light and comfortable, I often forgot it was there. In my opinion, the Flex is more comfortable to wear than the Jawbone Up, another well-designed and highly ergonomic wristband tracker.


Features and performance

The most recent fitness tracker from Fitbit, the Flex offers almost all the same features as the company’s One product. It relies on an internal accelerometer to record the steps you take, the calories you burn. The device calculates this by factoring in your age, height, and weight, which you punch into a linked Fitbit account online.

Another trick the Flex takes from the One is its ability to track the length and quality of your sleep plus how many times you woke during the night. The Flex is much more convenient gadget for sleep tracking, though, since it’s already strapped to your arm. That means you can wear it straight to bed and don’t have to mess with a separate armband like you do with the Fitbit One.

That said, the initiation process for kicking the Flex into sleep mode takes a little practice. You have to tap the device’s screen six times to tell it to start recording your Z’s. Only the right tempo of taps will work — go too fast or too slow and the Flex won’t register your input correctly. By contrast, the big physical button on the Jawbone Up (which also tracks sleep, steps, and calories) is much easier to manipulate.
One upside to the Flex is its LED screen, which displays how far you are towards your daily step goal. Just hit the screen once with your fingertip and the Flex shows your progress on a scale of one to five. When all five lights illuminate you’ve reached the default daily step quota of 10,000 steps. The device will even perform a happy dance when you achieve your goal, complete with haptic buzzing and all lights flashing in a random pattern.

Of course you can tailor your goals to match personal targets, too, but not from within the companion mobile apps (iOS and Android). To tweak your custom settings you need to log on to the Fitbit Web site. The Jawbone Up mobile application allows users to adjust their personal fitness targets for sleep and steps, though it lacks a Web-based UI.

I’ve long believed that the strength of the Fitbit system lies in its powerful online data analysis tools. Both the Fitbit mobile app and Web interface let you sift through your stats in views of days, weeks, months, and a full year. You can also pull from a large food database to log meals and count calorie intake. I especially like the ability to create custom foods, and have often-entered meals stored for fast entry. It makes the tedious task of calorie counting less onerous.

To measure weight in real time, Fitbit’s Aria Body Scale also talks to your Fitbit account and provides concrete data to pit against calories consumed and burned. Also, all of Fitbit’s current trackers, including the Flex ship with Bluetooth adapters to sync collected information wirelessly to PCs and Macs. That’s a trick the Jawbone Up can’t tackle. If you own a Samsung Galaxy S3 or Galaxy Notehandset, the Flex will also communicate directly with the Flex via Bluetooth.

Fitbit says the Flex has a rated battery life of 5 to 7 days depending on usage (i.e., how much you tap the screen). My experience mirrored these claims and was able to last approximately 5 days without needing to recharge. The Jawbone Up, however, has much longer longevity (about 10 days) since it transfers data through a more efficient (but less convenient) 3.5mm headphone jack.

Like the Fitbit One and Fitbit Zip, the Flex seemed very generous when logging my step counts. Many times a week I exceeded by 10,000-step goal by a few thousand. Sure, I live in New York, which can be very hectic, but somehow I don’t think I walk that much.


If you’re in the market for a personal fitness tracker to measure overall activity (plus how well you sleep), the $99.95 Fitbit Flex is an excellent solution. Sure, Fitbit’s own $99.95 One device does have all of the Flex’s core features and throws in stair tracking for good measure. That said, the One’s clip design has a tendency to fall off clothes, or stay clipped to them by accident. It’s also cumbersome to wear around the clock. Wristband-style trackers are much better suited for this type of duty.

That narrows the playing field to the pricey $149 Nike FuelBand and the slightly less expensive $129.99Jawbone Up. While the FuelBand is handsome and sports a real LED screen that can display text (and the time), it only works with iPhones and can’t track sleep. The Jawbone Up, on the other hand, logs sleep and steps, though it lacks a display. The Up also requires a physical connection to sync while the Fuelband uses proprietary (iPhone only) Bluetooth technology. By contrast, the Flex is comfortable to wear and has more features, including Bluetooth syncing (iOS and Android) and access to powerful analytical tools. That adds up to a solid fitness tech buy in my book. Of course, if you’re looking to save a little, the $59.95 Fitbit Zip is also a compelling budget choice.

The Fitbit Flex is a simple way to track steps, sleep, and calories. The Flex’s strap design makes it light and comfortable to wear. It also offers handy Bluetooth syncing, and Fitbit’s platform gives plenty ways to analyze your stats.


Clasping the Fitbit Flex’s strap shut is tricky. Direct syncing is only available with the iPhone, the Samsung GS3, and the Galaxy Note handsets.

Fitbit Flex Wireless Activity Plus Sleep Wristband, Pink
8 Total Score
Start from: $100.95

Never stop moving with fitbit flex. Wear this slim, stylish device all the time and get the motivation you need to get out and be more active. It tracks steps, distance, and calories burned shows you how you're stacking up against your daily goals. At night, it tracks your sleep cycle, helps you...

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0.6 x 0.4 x 8.2 inches ; 0.48 ounces

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4 ounces (View shipping rates and policies)

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Update 12/8/15 - Fitbit just added a new firmware update for the sleep timer feature. Once updated it's no longer necessary to tap the Fitbit before going to sleep or when waking it. It will now recognize when you're inactive and have gone to sleep. It also has some new goal setting software in the app relating to sleep to make it easier to focus on getting more (or less) sleep. The graphic interface is pretty nice. I'm looking forward to using this since I've become something of a night owl and could really stand to get on a better schedule. One more thing to like about my Fitbit.The update took about 5 minutes using my iPad and plugging my Fitbit into its charger while it updated. The whole thing was simple. A red arrow on the dashboard, in the sync area alerted me to the upgrade. I really like this new feature.I bought 3 of these fitbit flex devices, one for myself, my husband and my sister. Before purchasing I researched several wristband devices such as the Jawbone UP, the Nike Fuel and and the Polar Loop. I also looked at the fitbit force which is a newer version of this band. The lack of water resistance on the force was a deal breaker for me. I wanted to be able to wear this band 24/7 and to be able to wear it in the shower or when swimming. That was part of what made it attractive to me. Also, after reading reviews about the clasp problems on the force and how many people lost them, I wanted no part of that. They are also quite a bit bigger and look clunckier. The wristband on the UP looked like it would catch on everything and had no display at all. The Polar had lots of quality problems. I wasn't crazy about the looks of the Nike. The display is nice and I can see how people would like them, but not my style. The fitbit flex, to my tastes, had the coolest look. I also know a couple of people who own the fitbit flex and they were very enthusiastic about them so that influenced me as well.So here is what I like about the flex: I like the way it looks on my wrist. All of us got the slate color. You can also order bands in a few different colors, both here and on the Fitbit site. It is lightweight and even though I don't often wear a watch I don't notice this on my wrist at all. The clasp was VERY difficult to secure the first couple of times until the rubber softened up a bit and until I got the hang of it. I secured it off of my wrist a couple times when it was new. Making sure the band and clasps are lined up correctly and then placing one finger directly below the clasp and my thumb directly above and squeezing hard was the way to do it.I like that it's water resistant and that I can wear it swimming or in the shower. It is safe down to 10 meters or around 30 feet. I like that the wristband is made of TPU rubber, which according to Wikipedia is a type of rubber used in automotive instrument panels, caster wheels, power tools, sporting goods, medical devices, drive belts, footwear, inflatable rafts, and a variety of extruded film, sheet and profile applications. I think it should hold up for a very long time. I like that the display on the band gives me a rough idea by tapping on it of my progress throughout the day. I can also check my progress on my iPhone 4S and see number of steps so far, calories burned, how many hours of sleep I got last night and how often I woke up or was restless. So far it seems very accurate. I can also track the foods I've eaten and the calories, my weight goals and weight lost, check on the weekly number of steps friend's with Fitbits have taken and compare them with my own.I like that I can wear it 24/7 and only have to take it off to charge it once every 7 days. It takes about 3 hours to charge with a USB thingie that comes with it. I use a wall adapter to charge it but could also use a USB port on my desktop or laptop computer. I've lost too many pedometers in the past by dropping them out of my pockets or forgetting about them and sending them through the washing machine, so the wristband seems like a much better option for me. I also like that I can connect wirelessly with my smartphone and with the little dongle included that goes into my desktop or laptop, can connect with those wirelessly as well. Software downloads for all of these are free. I'm also able to connect on my first gen Kindle HD 8.9 although I can't see where it's shown as a supported device so far. But it works with the Android fitbit software in the app store.The step measurements seem reasonably accurate. Waving my hand slowly won't register as a step. Waving wildly will. Driving in the car won't register but reaching around quickly in the car sometimes will. Typing on the computer or Kindle won't register. I've heard that swimming doesn't register either but you can input the time and activity on your phone or tablet. When I first got the flex I started the iPhone app and watched my steps register on my screen as I walked around the house. That, and watching my steps on the treadmill have shown it to be pretty accurate for me, although not perfect. I think that all pedometers have some inaccuracies. What I'm looking for is a comparative trend where I can tell how much exercise I'm getting. The accuracy is good enough for me.So I wake up in the morning, tap the wristband quickly a few times to tell it I'm awake. Then if I tap it twice I see one tiny blinking light, telling me I'm working on my first 2,000 steps. Later, when I've hit that mark and tap to check again, I'll see one solid light and the second one blinking. There are 5 lights total and each represents 2,000 steps (or 20% of my goal. I could set it up differently on my computer, using a different number of steps as my daily goal if I wanted to.) So I can see my approximate progress any time during the day. When I hit my goal of 10,000 steps the band vibrates and all the lights flash. That means you done good!I can set up to 8 silent vibrating alarms on this fltbit. I have one to wake me up on weekdays (you can specify which days) and one at 8:00 each night to remind me stop eating for the day. The vibration gets my attention and is effective at waking me up. I set the alarms on my computer or phone.At night when I'm in bed and ready to go to sleep I tap the wristband rapidly a few times, it vibrates briefly, and goes into the sleep mode until I wake it again in the morning.So am I happy that I purchased the Fitbits for myself and my family members? Yes I am. It motivates me to walk or run more. I can connect to other friends and family with Fitbits to see everyone's weekly step progress but what really motivates me is just competing against myself. I'll find myself parking in the back of the parking lots at stores to log those extra steps or walking around the store longer because it's a good way to add even more. When I haven't reached my goal at night, I'll sometimes walk around the house several times just to hit a number. Now that can't be all bad, can it?Update 1/12/14 - I'll keep updating this review with comments and observations as I use this device. I noticed that walking at a rapid pace is counted as "active minutes". Someone on a message board suggested adding a touch of lotion to the clasp if you're having trouble getting it to clasp when it's new.Update 1/16/14 - A full charge is lasting just a bit over 7 days. It takes about 3 hours to recharge it fully.Update 1/21/14 - Some people have complained about this band coming undone and losing it. I haven't had any problems with it at all, even when pulling tight coat and shirt sleeves over it, brushing my arm against things or the dog pulling on it once or twice. (I'm sure the dog could have pulled it off if I didn't stop him.) The other day I had the dog's leash wrapped around the wrist with the Fitbit and even with the dog pulling against the leash the fitbit stayed on. We walked this way a couple of miles before I noticed it and unwrapped the leash from my wrist. But even with all that agitation my fitbit stayed put. It has stayed on through enough that I'm not very concerned about losing it. I've only taken it off to charge it. I have the band snug enough that I can only put one finger beneath the band but I can move it a couple of inches back and forth on my wrist.Update 7/3/14 - A new update that works with iPhones that use the Fitbit app was released a few days ago. I've used it with my iPhone 4S and really like the new upgrade. It adds a whole new dimension to my Fitbit app. With the upgrade, I just click on the exercise icon on the dashboard which takes me to a new screen showing the days of the week that I've exercised. (Meaning a walk, run or hike, something in addition to the regular walking in my daily activities.) This screen shows exercise frequency by day of the week, it puts a check on the days that you do some planned exercise. If I click the little stopwatch in the upper right-hand corner, it takes me to a screen where I can click Walk, Run, or Hike. I go back and can then click Cues which takes me to another screen where I can select whether or not I want to hear spoken cues. I can also tell it which cues I want including: Distance, Time, Average Pace, Split Pace, and Calories Burned. Then I go back again an can select the frequency of the cues from every .5 miles to every 5 miles. Or, I can make the cues time based ranging from every 2 minutes, 3, 4, 5, 10, 15, 20, 25, or 30 minutes. I can also select the volume of the cues. (Medium was perfect for me.) Then, back again to select a playlist from my iPhone's loaded tunes. Last, I allowed location services for Fitbit in my phone settings and I was ready to go. Now I see a big red circle with a Start arrow on the screen over a GPS map showing my location. I pop in my earphones, click Start and my music starts playing.As I walk, I can see a screen showing how far I've walked, rate per mile, time elapsed. Every half mile a voice interrupts my music telling me how far I've gone and all the other things I've specified in Cues that I wanted to know. Then it goes back to playing my music until it's time for my next designated Cue. How cool is that? It works seamlessly. At the end of my walk I tell it I'm finished (or I could also pause it if I stop to talk to a neighbor or something). When I'm finished (or even during the walk or run) I can see a little red line showing my route on the map. The steps from my walk are added to my steps count, just as they always are. I love these new features. They add a lot to the Fitbit experience.For those of you who track calories and foods eaten in the Fitbit app, the update now includes a bar code scanner. So far, the things I've scanned have been in their database. If you don't see the bar code symbol in the upper right-hand corner of the Log Food screen, log out of the Fitbit app and then log back in and it should be there.Update 11/28/14 - If something happened to ithis Fitbit today, what would I replace it with? Another one just like it. If one of the new Fitbit models was interchangeable with it on a daily basis I might get one of those too, just because I like new technology. But this one would be my main fitness band. I would like having a watch built in, but then it would look kind of silly wearing a conventional watch on the other arm. And I have a lot of nice watches.Update 12/12/14 - I just noticed today that the Fitbit Flex is the #1 Best Seller on Amazon this holiday season. It does seem like when I see people wearing fitness bracelets, this is the one they're most often wearing. A lot of the competitors have lowered prices significantly on their devices which is probably the best indicator of all. It's nice to know that I'm not the only Fitbit fan after wearing it for nearly a year. :)Update 12/26/14 - My Fitbit looks all new for the holidays. This replacement bracelet took over 20 days to arrive but for about $2 it was worth the wait.1pc Small S Black with White Dots Spots Replacement Band With Clasp for Fitbit FLEX Only /No tracker/ Wireless Activity Bracelet Sport Wristband Fit Bit Flex Bracelet Sport Arm Band Armband A couple people have asked me how the bands hold up over time. I have to tell them that I don't know since I'm wearing different colored ones almost every day. They don't have much of a chance to show wear.After almost a year of wearing these 24/7, none of us have had one come off accidentally. Even the cheap knock-off bands seem sturdy and reliable like the original. And I'm not a very careful person about pulling tight sleeves over it or draping grocery bag handles over my arm.I have the steps across our back patio counted out by counting them myself. It is 60 steps back and forth once. (Yeah, I know, way too anal.) Oftentimes when I haven't hit my 10,000 steps for the day, I'll go out and walk back and forth with my iPad on the patio table to check my progress. I know from doing this that the Fitbit step count is dead-on accurate for counting steps when walking. Dancing will add steps which I think is fair since it's at least as good as walking for exercise.Update 1/30/15 - I can't believe I've had my Fitbit Flex for over a year already. I'm still wearing it 24/7 as a great motivator to keep moving. I've had several people email me with questions about the way it counts steps so I thought I'd share this with you. I tested another fitness band recently, wearing it on the same arm as the Fitbit. The other band recorded a lot more steps than the Fitbit. I've "manually" counted steps while walking around different areas around my house and compared them to the Fitbit and found them to be exactly the same. But I never did it for more than about 100 steps. Now I was curious because the readings on the two bands were so different. So I went for a walk and counted out 1,000 steps as I took them, counting in my head. (Mumbling under my breath, actually.) Before I started, I noted the starting number of steps on my iPhone for both bands using the apps for each. At the end, I checked the number of steps for both bands. The Fitbit recorded 1004 steps. The other band recorded 1,217. Only 4 extra steps on the Fitbit is pretty impressive and is close enough for me. I'm contacting the manufacturer of the other band to see why it's so far off.Several people didn't realize that you can adjust the stride for the Fitbit. Just log into the dashboard in your Fitbit app, click on the little gear thingy in the upper right hand corner and select "Settings". There's a field there for Stride Length and Running Stride Length. You can manually enter your personal stride length. If you leave these blank, the app will estimate the values based on your height and whether you are a man or woman. Click the "Update Profile" button to save your changes. Remember to sync to update your tracker with the new stride measurements. I didn't even realize I could do this until several months after I had my Fitbit. I guess it must have estimated correctly in my case because when I put it in manually I didn't notice a difference.Update 4/30/15 - Fitbit has an update that now allows you to track multiple Fitbit devices on your Fitbit app. I haven't tried this, but from what I understand this will allow you to go back and forth between other models and once registered it will recognize them automatically. It's tempting to try the Fitbit Charge or the Surge that can measure heart rate or pulse or have caller ID. They're bulkier than I would like to wear on an all-the-time basis, but would be nice for workouts. And new technology is always fun. The Flex is still my first love and I like the switchable bands, but I'll look at the new models now that it isn't an either/or decision. Here are their instructions for adding another Fitbit:Update your Fitbit app (if you haven’t already)‘Set Up a New Fitbit Device’ from the Account tab in the Fitbit mobile app or Fitbit ConnectFinish the setup instructions, and start swapping – we’ll take care of the rest!Update 5/7/15 - Has everyone seen the new Fitbit commercial? I usually fast forward through TV commercials on the DVR, but this one I recorded and kept until I could find it on youtube: This makes me smile every time I watch it.Update 1/24/16 - When I purchased my Flex a little over 2 years ago it was advertised as being "Water resistant to 10 meters or 33 feet" which is 1 ATM. Their website now states: "Flex has been tested up to 1 ATM meaning it is sweat, rain and splash proof. However, the device is not swim proof. We also recommend taking Flex off before showering because, as with any wearable device, it’s best for your skin if the band stays dry and clean." The definition of 1 ATM, as I understand it is that it indicates that under static (nonmoving) conditions at 10 meters below the surface of the water the pressure of the water will not breach the seals on the device. But I can't take it into the shower? Perhaps even more confusing is the Fitbit Surge is rated at 5 ATM (50 meters) and has the same warning about not being swim proof and not to be worn in the shower. Are they just trying to ensure that users don't abuse the tracker?That said, I always shower with mine, I never dry it off afterward except the top when I'm drying my arms. I don't swim often but when I do, I leave it on. If I were going to spend a lot of time swimming on a regular basis I might take it off since it doesn't track swimming anyway. But for splashing around in a pool occasionally, I don't worry about it.My skin is somewhat sensitive to watch bands and I'm allergic to some metals and other materials. I couldn't be much LESS careful about the Fitbit and have never had a problem with the band and my skin. The underside is often damp from getting wet in the shower even half an hour later and it hasn't bothered my wrist. Being able to wear this 24/7 was a major selling point for me and it has worked just fine since January 2014.
January 11, 2014
Several asked my opinion of the Flex after I had compared UP to ONE last fall. I'm more pleased with Flex than expected. This review will be specifically for those comparing the Jawbone UP to the Fitbit Flex. For those interested in my review of the One and Jawbone UP it is located here: UP by Jawbone - Large Wristband - Retail Packaging - Onyx:---------------------UPDATE: I uploaded several head-to-head app screenshots.UPDATE: I've found that I am storing quite a bit of water in the Flex band pouch where the module goes. Even though they say it's shower safe, I'm pretty sure some funky stuff is going to be growing in there in a matter of time... But the band is replaceable!---------------------My journey with personal monitoring devices/pedometers started a LONG time ago: Before Fitbit even existed, with a device called the SportBrain. It was a traditional belt clip style so old that it plugged into a base that used a dial in phone modem to upload the usage data to a server. It was old. But my interest in devices that can help monitor and tell me about my activity started then, and we seem to be now in a golden age of personal data monitoring devices. Fitbit Flex, Jawbone UP, all of the Fitbit clip devices and so many more...Hardware itselfThe biggest drawbacks I found on the Jawbone UP were that it had no visual feedback about your daily achievement toward your goal and the fact that it had no visual battery indicator. It wasn't a problem for me personally, but for those who are hardcore driven on a daily basis to compare and achieve this could be a drawback for you. The next drawback about the Jawbone UP is that it does not wirelessly sync. You have to plug it into the headset jack of your phone to sync. If you are someone who wants data and feedback all day long, this would be a drawback.The Fitbit Flex does have visual feedback in the form of small white lights: They blink as you're charging, they have a special blink if you put it into sleep mode and provide 95% more feedback than Jawbone up. Jawbone UP does have status lights in it and they are used, but they could do a lot more with the lights they already have if they chose to.If you can throw a snap bracelet on, you can easily put on the UP. I did find myself fumbling a bit with the clip mechanism of the Flex like I do when I have to button my own shirt cuffs. After it was clipped though, it feels secure and I am not one to put on and remove devices like this. I want to set it and forget it.Fit & FeelThe Fitbit Flex feels very comfortable on the wrist. The pictures don't do it justice. For me personally this is the one defining factor that really makes the Flex shine for me compared to the Jawbone UP. It feels super light weight, doesn't grab, and doesn't look nearly as big/thick as the pictures make it look.The UP uses tension to stay on, while the Flex uses a clasp. The UP may have a better sense of solid attachment that wouldn't come off no matter how hard you fling your arm, but the inverse of that is the Flex: It doesn't have to monkey-grip your arm to be there and stay. You can have it fit a bit more loosely than UP and be comfortable.When typing on at a keyboard, I prefer the feel of the Flex. The rubber is flat and thin so it adds very little against the edge of a keyboard. The UP doesn't have the big square bump on the top, but it does have a bracelet shape/size all the way around, so it can prove a bit more of an annoyance up against a keyboard.The Flex does have replaceable bracelets and colors, which means the device is more convertible and flexible going forward. That being said, it is less visually appealing to me compared to the UP. The UP can be a part of jewelry and most people would never notice. The Flex does have a strange-ish future nerd look to it. I don't mind that, but some may.I wear both in the shower with no issues. I've done a lot of swimming pool roughhousing with the UP with no issues, but haven't tried with the FLEX. A commenter tells me that it is swimming approved, though the data provided might not be that useful.Battery Life & ChargingBoth the Flex and the UP charge in very similar almost identical USB adapters. They're meant to be charged on a computer and in my experience shouldn't be charged off of a phone USB wall charger. They both charged in similar amounts of time, and the Flex did last about 4 days on a charge. The UP can last as much as 10 days on a new battery, but I found that it has declined some since November. On this case, I say that both do about what they suggest. The UP fits snugly in the charger, while the Flex doesn't feel nearly as secure in its charger but I haven't had any issues with it falling out.Syncing:The Jawbone UP sync's via the headphone jack of the phone. It doesn't do Bluetooth, can't be plugged into a PC, so you're pretty much set on a smart phone or table to sync it. It's simple, doesn't consume battery to sync wirelessly, and works reliably. You have to watch because not all phones are supported.The Flex syncs wirelessly with Bluetooth 4.0 via the smartphone or via an adapter to a computer. For those without a smart phone or a locked down phone that work doesn't allow you to install apps, this could be a deal maker for you. It's not a constant sync but initiates as soon as you open the app on the smartphone. I haven't noticed any significant battery life loss. Not all phones are supported with Bluetooth 4.0-- most phones on the market don't yet have Bluetooth 4.0. You'll want to check Fitbit's website to see if your phone is supported. On the upside, the Flex does come with a Bluetooth adapter you can plug into a PC or Mac to sync wirelessly via the computer. It really adds extra work and decreases the usefulness of wireless sync, but it's do-able.Software:The software, to me, is the major differentiating factor between the two devices. The hardware looks entirely different, and there are some small differences in what the hardware can do, but the delivery through the app is what makes them clearly meant for different targets.The Jawbone UP software is beautiful. After you've sync'd enough it starts giving you feedback and encouragement through statistics. It will tell you "you were in the top 15% of UPpers this week" or "getting 8 hours of sleep per night it shown to improve...." if your sleep is coming up short. It does have the option to add in food consumption, performs a variety of tasks such as calibrating it's readings with actual distance walked, and has a really interesting "lifeline" feature that trends your activity & sleep over a period of hours, days, weeks and you can create a report on the fly comparing, for example, sleeping and calorie intake, to see if you consume more calories on days that you didn't have adequate sleep. It shows trends on daily/weekly and true to the marketing is a more "holistic" view of you and your life/activity. I guess we have reached my thesis for the comparison: Jawbone UP is about the holistic view of your life, while the Fitbit Flex is more finely focused on activity, seeing feedback for that activity in a quick frequent way and focusing on providing you that core data quickly and simply.The Fitbit software is the same software in use for all current Fibit devices. As soon as you launch it, a sync begins and your latest data will be presented. While the UP presents more current data on the "HOME" page, Fitbit has other tabs where you can explore the data they present. UPDATE: I discovered that the Fitbit software does do single activity trending if you turn the phone sideways: Hours/days/weeks, etc. It doesn't compare it to another statistic, but better than nothing.Both devices sync your data to a website. The Flex presents a more insightful view of your data on the website, while UP presents an equal amount of that data on the mobile app. Both support third party apps if you are really intense about a specific subject ( like food/calories with extensive catalogues, MyFitnessPal, etc.)A few features that the Flex has that the UP does not:-Lighted feedback on the band-more flexible fit, colors that can be changed after purchase-Thinner band around places you may bump against desks, etc.-wireless syncing (Jawbone needs to get on this train)-quick access in the app to 'water consumed'Fitbit Flex: Less expensive, simple quick device for activity & sleep tracking and wireless syncing from a company that is widely known for pedometers.A few features that UP has that Flex does not:-insight engine to look at your data and provide you feedback-longer maximum battery life-inactivity alarm. Fitbit could easily issue this in an update. I love this feature on the UP-bar code scanner in the food app to scan premade food for nutrition contents-power nap which will auto wake you between 25-45 minutes by modeling after your normal short sleep cycleJawbone UP: Technology that could pass for fashion. A fantastic app with a holistic view on your life, sleep and wellness.Both devices are good devices and had no fatal flaws. Both devices offer communities and ability to add friends to provide encouragement and interaction. If I had to give an elevator speech about the difference between the two:1. A few tech differences: Flex has wireless sync and quick feedback throughout the day. Flex is thick on top, and thin around. UP is more consistent without a clasp.2. UP has a very useful insight engine and is more of a "holistic" view. Less rewarding for someone who wants instant feedback. It's all about your time horizon: If you want to look at days and weeks of data, receive valuable feedback about your activity and sleep patterns and wellness the UP will probably please you most. If you are someone who wants hourly motivation and ability to sync frequently then the Flex is probably the right device for you.I hope this comparison has been helpful. If you have any specific questions I will be happy to answer or investigate & answer. My personal lean is toward the UP simply because I am using it to observe my sleep and activity from a bigger picture view. Sometimes I may go a day or few before I sync. If I were in a mode for physical fitness or weight loss, I may probably prefer the Flex. It all depends on your objective. There really isn't a fight between these devices-- they're both good and are focused towards different crowds.UPDATE: I found an interesting quirk with Flex: I was shopping at a store today and the shopping cart had a wheel that was a little bumpy. During my shopping I felt a vibration from Flex and thought maybe I had made a part of my daily goal. Then: BZZ, BZZ, BZZ! Turns out that the bumping of the cart in a rhythmic way confused the Flex into thinking I tapped it. It kept going in and out of sleep mode. Whoops. I can't wait until I see today's data....
May 17, 2013
1. I LOVE the fitbit.2. I like the interface.3. It's helped me lose weight and keeps me motivated.Why 3 stars?4. I bought it in August of 2016 and now, less than a year later, it's stopped working. I take very good care of it. It's never gotten wet or dropped. I don't overcharge it. For $7.50 a month it's a good deal given I've easily underspent my normal food buying because I use the fitbit, BUT I would have expected it to last more than 10 months.Will I buy another? Yes because it helps me keep track of what I do each day.But I think they should last longer than 10 months.
June 12, 2017
Fitbit Flex review: A most versatile, feature-packed tracker
8 Total Score

Ease of use
Design and form factor
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1 Comment
  1. Reply Samantha June 19, 2015 at 10:31 am

    I had the Fitbit and it’s main weakness is the proprietary charger. I’ve had two go out on me already and I’m done with it now.

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