How Accurate Is Fitbit?

How well are your calories, steps, and more being tracked?

Fitbit is the world's most popular activity tracker, calculating your daily activity while motivating you to move throughout the day. But how accurate is a Fitbit? Learn how Fitbit calculates your steps and how well it keeps tabs on steps taken, calories burned, and sleep.

How Does Fitbit Work to Track Your Steps?

Fitbit uses a accelerometer with three axes that can detect movements in any direction. When worn on the body, the data captured by the Fitbit's accelerometer is analyzed by a proprietary algorithm that looks for specific patterns of movements.

Together, the data from the accelerometer and the counting algorithm determine the number of steps taken, distance covered, energy spent, the intensity of exercise, and sleep.

How Accurate Is Fitbit?

Fitbits are considered to be surprisingly accurate, but they're not perfect. Because movement is subject to different factors, they're known to undercount or overcount steps at times. Walking on a plush carpet or pushing a shopping cart or stroller may cause Fitbit to undercount steps. Driving down a really bumpy road or riding a bike may cause it to overcount steps.

Fitbit family
Fitbit 

According to a study on Fitbit accuracy published by the NCBI, researchers found that Fitbit devices were “acceptably accurate” for step counting about 50% of the time. Additionally, they found that accuracy increased depending on where the device is worn:

  • For jogging, wrist placement was the most accurate.
  • For normal-paced walking, wearing the Fitbit on the torso provided the most accurate measurements.
  • For slow or very slow walking, placing it on the ankle provided the best accuracy.

On the other hand, Fitbits aren't great at calculating energy expenditure (i.e., calories burned and workout intensity). They have a tendency to overestimate higher-intensity activities, while underestimating distance traveled with fast walking. But for sleep tracking, Fitbit devices were on par with research-grade accelerometers—in other words, accurate.

Based on a 2017 study, the Fitbit Surge was determined to be significantly more accurate in counting calories than the Apple Watch, Basis Peak, Microsoft Band, Mio Alpha 2, PulseOn, and Samsung Gear S2.

How to Increase the Accuracy of Your Fitbit

If you're concerned your Fitbit isn't tracking your activity properly, or you want to ensure the most accurate results, here are the steps you can take to help increase the accuracy of your Fitbit.

Wear Your Device Correctly

Where and how you wear your Fitbit can impact accuracy. In general, the device should be remain in close contact with your body when you're exercising (and not dangling from a necklace, backpack, or loose clothing).

Here's what Fitbit recommends:

  • For wrist-based Fitbits: Wear your Fitbit watch on top of your wrist, not too tight or too loose. For devices that track heart rate, make sure it's touching your skin, and wear it a bit tighter on your wrist when working out.
  • For clip-based Fitbits: Wear the Fitbit close to your body with the screen facing outward. Secure the clip tightly to any part of your clothing. Experiment with different locations to see what works best for you (more secure is better).

Change Your App Settings

Fitbit relies on the information you provide in the app to accurately calculate your steps taken and daily activity.

Woman wearing Fitbit holding a ball
Fitbit

Make sure the following settings are set up correctly in the app. These settings can be found on your dashboard, either under Device Settings or Personal Information.

  • Wrist orientation: By default, Fitbit is set to your left hand, i.e., most people's non-dominant hand. If you're wearing it on your right hand, update this setting to Right.
  • Height: Fitbit uses height to estimate your walking and running stride lengths. Enter your correct height in inches or centimeters to ensure the most accurate step count.
  • Stride Length: Fitbit uses a default stride setting based on your height. For greater accuracy, change this and manually enter your stride length. See How Does Fitbit Track Steps to learn how to do this.
  • Exercise App: To better measure workout intensity, use Fitbit's exercise app (certain models only) to track your workouts, especially for activities like spinning or yoga. The app has an Android, iOS, and Windows version.
  • Use the GPS: If you're not swinging your arms when walking (for example, when pushing a stroller), you can use Fitbit's GPS feature to better calculate your daily activity (certain models only).

Change Where You Wear Your Fitbit

Based on the research cited above, you can potentially increase the accuracy of your Fitbit by changing the location of where you wear your Fitbit during certain activities.

  • When walking at a normal pace, wear the Fitbit on your torso (clip models).
  • When walking very slowly, wear the Fitbit on your ankle (clip models).
  • When jogging, wear the Fitbit on your wrist (wrist models).
  • When sleeping, Fitbit suggests wearing a classic wristband (wrist models).

Generally speaking, you shouldn't sweat your Fitbit's accuracy too much. Unless you're relying on a Fitbit for making health-care decisions, being off a few steps or calories won't noticeably affect the use and enjoyment of your device.