Shouldn’t Fitness Trackers Be Accurate?

314xSphvUfLI’ve written about fitness trackers here several times. I currently have a Fitbit Charge, I’ve reviewed the Fitbit Flex, Fitbit One and Jawbone UP24, and I tried the Nike+ FuelBand.

One problem with these devices – aside from comfort, which is not always a given – is their accuracy. I’m surprised that most websites that review these devices don’t even discuss accuracy, when it’s not that hard to compare different fitness trackers, and determine how accurate they are. It’s almost as though reviewers expect them to be inaccurate, and don’t think that accuracy is important. (One notable exception is this Mashable review.)

I’ve been using the Fitbit Charge for a few weeks, and I’m surprised at how inaccurate it is. Fitbit, on their website, tout the accuracy of the device, saying:

“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.”

Yet it’s horrible. Compared to the Fitbit One, the Charge records 30-50% more steps, and, therefore, longer distance and more calories burned (and its “active minutes” is pretty wonky too). It even records some steps while I sleep. Granted, the Fitbit Flex records lots of steps when you drive, so I guess this is an improvement. And the Jawbone UP24 doesn’t record steps when you walk on a treadmill, so all the Fitbit devices win on that front.

Here’s another example of the Fitbit Charge getting it wrong. I went out to mail some letters today; the mailbox is 400m away. First, when putting on and tying my shoes, the Charge recorded 20 steps. Then, I set the Fitbit app to record my walk. When you do this, it uses the GPS in the iPhone (or other phone) to record a map of your walk, providing you with distance, time and pace per mile or kilometer. The app recorded this correctly, and said I had walked 794 steps; the Charge recorded 943 steps.

Most people don’t compare the accuracy of different devices, so they never know how inaccurate their devices may be. Precise accuracy isn’t essential; as I said in my review of three of these devices:

“Fitness trackers are motivators. While, on the surface, they claim to record data about your activity, the real reason people buy them is to motivate themselves to be more active. None of them are perfectly accurate, and they all have drawbacks.”

Thinking about this made me wonder how companies think they can sell these devices with such glaring inaccuracy. I understand the technical hurdles in counting steps using a wrist-worn device; but what Fitbit says, above, is that it’s not only possible, but accurate. They say that the charge “may count a few more steps,” but they’re disingenuous if they really think that it’s only a few steps.

Fitbit says:

“Fitbit is dedicated to developing the most accurate activity trackers on the market. Our team performed multiple internal studies to rigorously test the accuracy of our trackers. Through our testing, we have confirmed that our trackers are some of the most accurate wireless tracking devices.”

And, on another page:

“We’ve tuned the accuracy of the Fitbit tracker step counting functionality over hundreds of tests with multiple body types. All Fitbit trackers should be 95-97% accurate for step counting when worn as recommended.”

So the problem is one of a marketing message that is simply not true; where I grew up, we called that “lying.” 95-97% accurate would be great, if it were true. Assuming that the Fitbit One is the most accurate of the devices I’ve tested, because it’s worn on your belt, like a standard pedometer, none of the other devices are anywhere near that accuracy. The Nike+ FuelBand cops out, most likely because the company realized that accuracy is simply not possible with a wrist-worn device; they came up with “Nike+ Fuel,” a points-based system that has no relationship to steps. In a way, they’re the most honest; they don’t pretend to be accurate. However, Nike still claims that their software can count calories using an algorithm based on the energy you expend when you move. That’s pretty vague, and deflects the issue.

The fitness tracker sector is expanding rapidly, and the one thing companies should do is ensure that their devices are accurate. I think these devices do have a future, but only if we can take them seriously. For now, we simply cannot.

28 thoughts on “Shouldn’t Fitness Trackers Be Accurate?

  1. Did you calibrate the Fitbit before doing those tests? AFAIK the 95-97% claim is after doing the calibration, which you can read how to do on their website. For most “average” people they don’t need to do the calibration process, but I can’t imagine them being very accurate without it.

    It’s fairly straight forward, just a walk of a known 20m length and then another for running. I’ve had to do that with every pedometer I’ve owned since ’98, so I thought that was standard process. Sorry if you did this already, but you didn’t mention it anywhere, so I thought I’d chip in.

    • The accuracy I’m seeing is regarding the step count.

      There is no “calibration.” What you can do is measure your stride length; whether you do or not has little effect an accuracy, for several reasons. First, your stride length isn’t the same all the time. When I got the Fitbit One two years ago, I lived in a house with tiles, and it was very easy for me to measure my stride, since all the tiles were 30 cm. I set my stride to 80 cm.

      But, recently, I wanted to check that. On my treadmill, I walked exactly one mile, and calculated then, based on the number of steps I walked, that my stride was 100 cm. Then I walked to a mailbox and back; 800 m total, measured by GPS. In that case, my stride was 90 cm. And when you walk slower – normal walking at home or in an office – it’ll be even shorter. But, again, I’m not concerned by the distance, I’m more interested in the step count, as that should be accurate.

      An aside: I find it surprising that one review I read of the Charge pointed out that the distance of a known route wasn’t accurate; as you say, you need to enter the stride length for that to be accurate, but no matter what, it won’t be unless you’re using the Track Exercise feature, which uses the GPS in your phone.

  2. Did you calibrate the Fitbit before doing those tests? AFAIK the 95-97% claim is after doing the calibration, which you can read how to do on their website. For most “average” people they don’t need to do the calibration process, but I can’t imagine them being very accurate without it.

    It’s fairly straight forward, just a walk of a known 20m length and then another for running. I’ve had to do that with every pedometer I’ve owned since ’98, so I thought that was standard process. Sorry if you did this already, but you didn’t mention it anywhere, so I thought I’d chip in.

    • The accuracy I’m seeing is regarding the step count.

      There is no “calibration.” What you can do is measure your stride length; whether you do or not has little effect an accuracy, for several reasons. First, your stride length isn’t the same all the time. When I got the Fitbit One two years ago, I lived in a house with tiles, and it was very easy for me to measure my stride, since all the tiles were 30 cm. I set my stride to 80 cm.

      But, recently, I wanted to check that. On my treadmill, I walked exactly one mile, and calculated then, based on the number of steps I walked, that my stride was 100 cm. Then I walked to a mailbox and back; 800 m total, measured by GPS. In that case, my stride was 90 cm. And when you walk slower – normal walking at home or in an office – it’ll be even shorter. But, again, I’m not concerned by the distance, I’m more interested in the step count, as that should be accurate.

      An aside: I find it surprising that one review I read of the Charge pointed out that the distance of a known route wasn’t accurate; as you say, you need to enter the stride length for that to be accurate, but no matter what, it won’t be unless you’re using the Track Exercise feature, which uses the GPS in your phone.

  3. I”m having the opposite problem. My Charge didn’t record a single step yesterday when I walked around Costco for an hour pushing a shopping cart (even though the web site says it will log steps when pushing a shopping cart or stroller). Tonight, I measured it against my Fitbit One when I was out walking, and the One was spot on, while the Charge consistently gave me 10-20% fewer steps. It also doesn’t register any steps when I’m carrying something in my left hand while I walk. I’ve only had it a few days, and I’m wondering if I got a dud.

  4. I”m having the opposite problem. My Charge didn’t record a single step yesterday when I walked around Costco for an hour pushing a shopping cart (even though the web site says it will log steps when pushing a shopping cart or stroller). Tonight, I measured it against my Fitbit One when I was out walking, and the One was spot on, while the Charge consistently gave me 10-20% fewer steps. It also doesn’t register any steps when I’m carrying something in my left hand while I walk. I’ve only had it a few days, and I’m wondering if I got a dud.

  5. I have been going back and forth with Fitbit over the Charge. It is totally inaccurate and I have changed the stride, reset and they ask me to do all of these step measurements and still the miles and steps are underestimated. They told me I should not hold on to the handles of the treadmill – which I never do anyway. I am still going back and forth and am just ready to throw it out.

  6. I have been going back and forth with Fitbit over the Charge. It is totally inaccurate and I have changed the stride, reset and they ask me to do all of these step measurements and still the miles and steps are underestimated. They told me I should not hold on to the handles of the treadmill – which I never do anyway. I am still going back and forth and am just ready to throw it out.

  7. I am also unhappy with my Fitbit Charge. I measured a new route to walk with my car and it should show that I walked 1.6 miles but it shows 1.19. This is not what Fitbit advertises to me as accurate

  8. I am also unhappy with my Fitbit Charge. I measured a new route to walk with my car and it should show that I walked 1.6 miles but it shows 1.19. This is not what Fitbit advertises to me as accurate

  9. I too am having trouble with it counting enough steps. I ran/walked 12 miles the other day and only recorded it as 10.45. Very frustrating my friend uses the nike app and it it always accurate with our mileage.

  10. I too am having trouble with it counting enough steps. I ran/walked 12 miles the other day and only recorded it as 10.45. Very frustrating my friend uses the nike app and it it always accurate with our mileage.

  11. I have the Fitbit Charge HR. I’m a truck driver and it records my driving several hours a day as steps. I have tried it on both wrists, and other than taking it on and off as I drive, it is very frustrating. I can edit my activity settings, but that means everytime I stop and start I have to go in and manually change things. This is a major flaw as far as I’m concerned!

  12. I have the Fitbit Charge HR. I’m a truck driver and it records my driving several hours a day as steps. I have tried it on both wrists, and other than taking it on and off as I drive, it is very frustrating. I can edit my activity settings, but that means everytime I stop and start I have to go in and manually change things. This is a major flaw as far as I’m concerned!

  13. My Fitbit said I was taking steps when I was just standing in place and swinging my arms. Half the time it wouldn’t even calculate that I went upstairs. I paid $150.00 for a cheap watch. False advertisement as far as I’m concerned.

  14. My Fitbit said I was taking steps when I was just standing in place and swinging my arms. Half the time it wouldn’t even calculate that I went upstairs. I paid $150.00 for a cheap watch. False advertisement as far as I’m concerned.

  15. My Fitbit Charge HR is crap as well. I literally sat at my desk all day and it said I walked 9,500 steps. I am so frustrated I paid $150 for this crap and nit planning on people in all the extra effort required to rig it.

  16. My Fitbit Charge HR is crap as well. I literally sat at my desk all day and it said I walked 9,500 steps. I am so frustrated I paid $150 for this crap and nit planning on people in all the extra effort required to rig it.

  17. Just got a Fitbit Flex. Stood in one place and moved my arm back and forth 10 times…it recorded 30+ steps. Makes me seriously question the accuracy.

  18. Just got a Fitbit Flex. Stood in one place and moved my arm back and forth 10 times…it recorded 30+ steps. Makes me seriously question the accuracy.

  19. I just purchased the Fitbit Charge 2 hr and used it for the first time. I am a school bus driver and during my 3 hour DRIVE, I had 6000 steps! To me the inaccuracy defeats the purpose of having a fitness tracker.

  20. I just purchased the Fitbit Charge 2 hr and used it for the first time. I am a school bus driver and during my 3 hour DRIVE, I had 6000 steps! To me the inaccuracy defeats the purpose of having a fitness tracker.

  21. So putting the fitbit in my pocket while I’m walking on the treadmill gives me the miles pretty accurately. Not sure why it doesn’t work on my arm but I’ll do it if it works.

    • It depends on how much you swing your arms. Some people don’t move their arms much on a treadmill, so a tracker can’t do much.

  22. So putting the fitbit in my pocket while I’m walking on the treadmill gives me the miles pretty accurately. Not sure why it doesn’t work on my arm but I’ll do it if it works.

    • It depends on how much you swing your arms. Some people don’t move their arms much on a treadmill, so a tracker can’t do much.

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