Wearable Review: Fitbit Charge Activity Tracker

Update: Having discovered serious problems with the accuracy of this device, I’ve updated my review on January 2, 2015. I leave my original review intact below.

In my original review of the Fitbit Charge, which you can read below, I said, “it’s as accurate as the Fitbit One.” I’ve come to find that this is not the case.

I originally bought the Fitbit Charge when it was released in the UK. On December 26, Amazon UK had a one-day sale, offering the device at 25% off. I ordered one, and returned the original device. While the original device was fairly accurate in my testing, this new device is terribly inaccurate.

Here are some examples. One day, I tested the devices by wearing both of them. I went about my usual business, and I walked on my treadmill for 30 minutes. Both devices recorded nearly the same number of steps on the treadmill (2,048 steps for the Charge, and 1,997 for the One), but for the rest of the day, the numbers diverged greatly. Near the end of the day, when the Fitbit Charge was at 5,000 steps, the One was almost exactly at 4,000 steps. These convenient numbers make it very easy to calculate the discrepancy between the two devices. If you take away the 2,000 steps on the treadmill, where the devices nearly matched, the Charge recorded 3,000 steps, and the one 2,000. In other words, the Charge is recording 50% more steps than the One. (I’ve noticed that the Charge records some steps when I’m asleep; a half-dozen here, a dozen there, adding up, some nights, to 50 steps or so. And, no, I don’t sleepwalk.)

In subsequent days, I saw similar numbers. The Charge generally records from 30-50% more steps. What this means is that the distance it tells you you’ve walked is 30-50% higher than what you actually walked (or ran), and the calories that it says you burn are much higher than what you have really burned. (Not 30-50%, because the Fitbit also takes into account your basal metabolic rate, or the number of calories your body burns if you do nothing.)

But it goes much further than that. Today, I walked on my treadmill for exactly 30 minutes. When I started, there were no active minutes recorded; when I finished, there were 35 active minutes recorded.

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Looking back, I see that this is the case almost every day. Yesterday morning, it recorded 6 active minutes when I went downstairs and made breakfast. And the day after the above 35-active-minute workout, the Charge recorded 27 active minutes for the same 30-minute walk on my treadmill.

Not only is the device reporting incorrect information, but the Fitbit website is also presenting incorrect past statistics. Looking back, I see that my step counts are grossly over-exaggerated. In March of this year, it shows me as having gone over 20,000 steps several times. I was using the Fitbit One, which seems very accurate, but here it looks as though the website algorithm – which is probably what takes the raw data from the devices, and converts it into numbers – is way off base. There’s no way of knowing if this is what’s causing the discrepancies between the two devices, but if it were the overall algorithm, then both devices would report incorrect numbers now, and that’s not the case. When I look back at active minutes, I also see this. I’m not a very active person, working at home in a sedentary job, and there’s no way that my activity was anywhere near what is shown in the screenshot below.

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An article on the Fitbit website discusses the accuracy of the device. It says:

“Charge has been tested extensively against our clip-based devices like the Fitbit One and Fitbit Zip. That said, because Charge is specifically designed for your wrist, if you move your body a lot and not your arms (or vice versa), you may get a slight difference in activity than you would see on your clip-based trackers. Additionally, since you’re more likely to wear Charge 24/7, you may count a few more steps.

“This is no different than any wrist-based tracker on the market. For most people, there may be no difference at all between clip and wrist based trackers or it may be within a few percentage points difference. That said, if you have a lifestyle where you move your hands a lot such as playing the drums every day, you may see a few extra steps on your Charge because we do want to give you credit for this activity.”

If it were just “a few extra steps,” I would understand. But this is much more than a few. And that doesn’t explain why 30 active minutes count as 35; that’s something that you simply don’t get wrong because the device is worn on the wrist as opposed to on the belt.

With this in mind, I strongly recommend avoiding the Fitbit Charge, if you seek a device that is accurate. While the first model I had was quite accurate, the fact that the second is so far off suggests that there is a serious problem with the quality of these devices. It’s pretty much a crap shoot as to whether the device you get is accurate. If you do buy one, I strongly suggest you check its accuracy. You can do this by, for example, counting your steps per minute on a fixed-speed treadmill, or even outdoors on a flat surface, then extrapolating to get the total steps for the amount of time you walk. You can also check the distance by walking around a track, if you have access to one. The way the Fitbit calculates distance is by simply multiplying the number of steps you take by your stride, and you can set that in the settings on the Fitbit website, in the Personal Info section. You can measure your stride by taking a number of steps along a distance that you can measure, such as in a room whose dimensions you know. (I suggest that you measure this over at least ten steps.)

I contacted Fitbit’s PR firm, who sent me another Charge. I wore two charges on the same wrist for two days, and they both gave more or less the same numbers (one was a tad higher than the other). So it’s not just a single bad unit, it’s the Charge in general that’s inaccurate. I’ll stick with the Fitbit One.

Original review:

I’ve been using the Fitbit One fitness tracker for about two years. It’s easy to use, since it clips on your belt and you can forget about it. But I like the idea of the fitness tracker, and have tried several others, such as the Nike+ Fuelband, and the the Fitbit Flex and Jawbone Up 24. I found that all of these trackers – with the exception of the Fitbit One, were inaccurate, and many were uncomfortable.

314xSphvUfL.jpgFitbit has released a new fitness tracker, the $130 or £99 Fitbit Charge. (Amazon.com, Amazon UK) This device is similar to the Fitbit Flex, but with a larger OLED display that can show the time, steps taken, distance travelled and more. Unlike the Flex, however, the Charge is very accurate. When I tried the Flex for a few days, I found its numbers diverged widely from those of the Fitbit One, especially when walking on a treadmill, or when driving in a car; it counted about 100 steps during a 15-minute drive, for example. A waist-worn tracker is probably the most reliable in counting steps, and the One is a good benchmark. Fitbit seems to have greatly improved the accuracy here, making the Charge seem much more accurate than its predecessor, and than the Jawbone Up 24, which was also very inaccurate.

2014-12-11 09.53.05.pngThe Fitbit Charge records your steps, floors you climb (using an altimeter; 10 ft = 1 floor), your “active minutes,” and your sleep. Using steps, it gives you a rough idea of the distance you’ve travelled. It also calculates the number of calories you have burned, based on your activity; you can log food as well, to determine how much you’ve eaten, and set a goal of burning more calories than you consume each day. You can record your weight, either by entering it manually, or by syncing with Fitbit’s Aria scale. (Amazon.com, Amazon UK) (I use one of these, and it’s easy to use, and syncs to your Fitbit account over Wi-Fi.)

You can also record walks or runs, using the Fitbit iOS app. This records your distance, splits by mile or kilometer, and, using the iPhone’s GPS, even saves a map tracking your route. You initiate a recording by using the Track Exercise section of the iOS app, and choose Walk, Run or Hike. You can also start this by pressing and holding the button on the side of the Charge for a few seconds.

Fitbit’s iOS app is the best of the fitness apps I’ve seen, as compared to those of Nike, Jawbone and Withings. It can display lots of information, and lets you set goals. When you reach your goal – which can be steps, distance, calories burned, active minutes, floors climbed or a calorie deficit – the Charge vibrates to tell you. And the Fitbit website has a graphical dashboard that shows all of your data.

Fitbit web

All this can seem a bit finicky; you may not want to view all of this data, and you can choose what to display, and in what order, in the Fitbit app. There are also a number of customization options for the device itself, which you can set from the app:

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You can see above that there is a tap gesture; this lets you choose what displays when you tap twice on the device. I found this very hard to get right. I initially wanted to double-tap the way I double-click a mouse, but that didn’t work; I had to tap very hard to get the device to display. I eventually found that you need to double-tap fairly slowly to get it to work, and I’ve gotten used to it, but figuring that out wasn’t easy, and the Fitbit website offers no help on this matter. (I just tried it again, as I was writing this article, and it took four tries to get it right; Fitbit needs to fix this.)

While much of the data the Charge records and displays is useful, I’m not convinced that the sleep data tells me much. Unlike previous Fitbit models, where you had to manually engage a sleep mode, this one detects when you go to sleep by the fact that you’re not moving. And the sleep data it offers is sketchy at best. Since it’s based on your movement, you may be awake and not sleeping while the device thinks you are asleep.

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The Charge also offers two useful features, but that could be better implemented. It has a vibrator that can alert you to incoming calls, and the display shows caller ID. This is great, except it only vibrates once. If you miss that vibration, and don’t hear your phone (mine is generally set to silent), it ends up being useless. It should continue vibrating until you’ve picked up the call. You can also set “silent alarms,” which vibrate – and continue – at times you set in the Fitbit iOS app. It takes too many steps to get to the alarm settings, and it would be more useful if you could set them more easily. You can set repeating alarms, which is good if you get up every morning at the same time, but they can only repeat daily. So if you want to set an alarm for every day of the week, you need to set five alarms. And not forget to turn it off on holidays or when you’re on vacation.

As for the device itself, it’s comfortable, having a soft plastic strap that is thin enough that it doesn’t get in the way when I’m typing, as the Jawbone Up 24 or Nike+ Fuelband did. It comes in two sizes; I have big bones, and the large model just barely fits. You need to leave a finger’s thickness between the band and your wrist to be able to attach the device by pressing its stainless steel clasp against the underside of the wristband, and I can just barely squeeze my finger under it. I would have liked a slightly larger model, which would be a bit looser. The Fitbit website only says there are two sizes, but the product manual says there is also an extra large size, and I’ve contacted Fitbit to find out how one can purchase that model, and if I can exchange mine. (I bought it from Amazon, so I know I can return it.) If you’re hesitant about the sizes – small is 5.5″ – 6.7″, and large is 6.3″ – 7.9″ – opt for one that’s larger than your wrist, and if you have a large wrist, contact Fitbit. (If I get more information about the extra large size, I’ll add it here.)

Fitbit has another version of this coming out in a couple of months, the Fitbit Charge HR. This will cost a bit more, and will have a heart rate sensor, to record your heartbeat continuously. I don’t really need this. And the Fitbit Surge, which will be larger, more like a Pebble watch, will also include GPS; again, not a feature I need, since my iPhone can handle that.

One note about syncing the device. There are two ways to sync: using the iOS (or Android) app, or using a dongle, provided with the device, which you connect to your computer. The former works fine; the latter hasn’t worked for me, even with the Fitbit One, for some time. Several months ago, it stopped working, and Fitbit sent me a new dongle; that worked for a while, then stopped. I have been unable to get the desktop software to sync the Charge, even though I re-installed the software. It seems to think that the Charge I have is a different one than the one linked to my account (which I’ve synced using my iPhone), and fails. I find that the desktop software is problematic, at one point, causing high CPU usage, and Fitbit support is not too helpful regarding these issues.

While I haven’t had it long, I like the Fitbit Charge. I actually find it useful to be able to check the time on my wrist; I haven’t had anything that allowed me to do that for a long time, but I’m finding that I do use it as a watch. The device is comfortable, and it’s easy to forget that I’m wearing it. It’s not the most attractive of devices, but it looks much better than, say, the massive Nike+ Fuelband, or the oddly-shaped Jawbone Up 24. And it’s as accurate as the Fitbit One. I’m still tempted by the Withings Activité, which looks like a real watch, but, for now, the Fitbit Charge is a keeper.