How Does Fitbit Track Steps?

Turning your motion into data

Have you ever wondered how a Fitbit tracks your steps and other activities? It uses accelerometer technology to turn your footsteps and other movements into data, providing detailed information about your exercise habits. Here's more about how Fitbit steps are measured.

How Does Fitbit Track Steps?

Fitbit uses a 3-axis accelerometer along with a step counting algorithm to keep track of your steps and other movements. When worn on your body, the accelerometer converts your physical movements into digital measurements.

Someone wearing a Fitbit device showing a steps count.
@maxeyvons via Twenty20 

By analyzing these digital measurements, your Fitbit can provide surprisingly accurate information about the patterns and intensity of your workouts, including:

  • The number of steps taken
  • The distance traveled
  • The number of calories burned
  • The intensity of the workout
  • If you're biking or swimming (on certain models)

How Does an Accelerometer Work?

Accelerometers are tiny devices that can detect the direction of movement by sensing changes in gravity. They're found in a wide range of every day technology, including smartphones and game controllers. That's why the screen rotates with you when you turn your phone sideways. That's an accelerometer at work.

Accelerometers rely on a technology called MEMS (Micro Electro-Mechanical Systems). A MEMS is a tiny machine that can convert movement into an electronic signal which is read by a sensor. In order to track motion in many directions, the accelerometer must have multi-axis sensors. Fitbit's accelerometer has three axes (not just one, like old style pedometers), which means it can track movements in any direction.

How Does Fitbit's Step Counting Algorithm Work?

Along with an accelerometer, Fitbit has a finely tuned algorithm for counting your steps. The algorithm looks for motion patterns that are indicative of walking and meet a certain detection threshold. If the pattern and magnitude of the motion meet the standard set by the algorithm, it's counted as a step. If you're just tapping your hand on the desk, it won't count as walking.

The data gathered by the accelerometer and counting algorithm are used to calculate surprisingly detailed information about your workout, which is then uploaded to your app when you sync your Fitbit. However, the algorithm isn't perfect. Fitbit has been known to undercount steps, for example, if you're walking on a soft surface, such as plush carpet. It may also over count steps at times, for example, if you're driving down a really bumpy road.

How to Make Your Fitbit Count Your Steps More Accurately

Plush carpets aside, there are ways to increase the accuracy of how Fitbit is counting your steps. For starters, it's important to manually enter your stride length in your Fitbit app, especially if your stride is longer or shorter than average. Otherwise, Fitbit will use default data based on your height, which may not match your actual stride at all.

To measure your stride length:

  • Pre-measure an area (in inches or centimeters) where you can take at least 20 steps, such as your driveway or a long hallway.
  • Count your steps as you walk across the pre-measured distance, walking at least 20 steps at a normal pace.
  • Divide the total length of the pre-measured distance (in inches or centimeters) by the number of steps you took. This will provide your stride length in inches or centimeters.
  • In the Fitbit app, go to Settings > Personal Info > Stride Length to enter your stride length.

Note that you can also calculate your running stride. Just run, instead of walk, when measuring your stride length. Once you have your stride length, you can enter the data into the Personal Info screen of your Fitbit app, as shown below. Be sure to select Submit to save the information.

Entering Fitbit Stride length