How does my Fitbit device calculate my daily activity?

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Your Fitbit device uses sensors and algorithms to calculate and report your daily stats.

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How does my Fitbit device count floors?

Fitbit devices that count floors have an altimeter sensor that can detect when you're going up or down in elevation. Your device registers one floor when you climb about 10 feet at one time. It does not register floors when you go down.

Fitbit devices do not count the elevation gains simulated from a StairMaster, inclined treadmill, or other stationary exercise equipment. Your device uses changes in barometric pressure to detect elevation change, and therefore requires that you physically change elevation in order to properly record floors.

How does my Fitbit device count steps?

Fitbit devices use a 3-axis accelerometer to understand your motions. An accelerometer is a device that turns movement (acceleration) into digital measurements (data) when attached to the body. By analyzing acceleration data, our devices provide detailed information about frequency, duration, intensity, and patterns of movement to determine your steps taken, distance traveled, calories burned, and sleep quality. The 3-axis implementation allows the accelerometer to measure your motion in any way that you move, making its activity measurements more precise than older, single-axis pedometers.

Fitbit devices have a finely tuned algorithm for step counting. The algorithm is designed to look for motion patterns that are most indicative of people walking. The algorithm determines whether a motion's size is large enough by setting a threshold. If the motion and its subsequent acceleration measurement meet the threshold, the motion will be counted as a step. If the threshold is not met, the motion won’t be counted as a step.

Other factors can create enough acceleration to meet our threshold and cause some over counting of steps, such as riding on a bumpy road. Our engineers have worked diligently on your tracker's algorithms to make sure that it does not pick up false steps or activity recordings while in a car. Unless you are driving in a car with a stiff transmission or on back country roads, your tracker should not give you credit for any work that you don't do. If you do pick up some steps while driving, see How do I edit or delete Fitbit data and activities? for instructions on removing steps.

Your device may register movements or restlessness as steps when you're wearing it while you sleep. The number of steps typically measured during these periods is minimal, and should not offset your overall fitness progress. Any steps taken to and from other rooms during the night will also be tracked. Equally, it's possible for the algorithm to undercount (not meet the required acceleration threshold). Examples here include walking on a very soft surface such as a plush carpet.

For information about specific conditions see How accurate are Fitbit devices?

How does my Fitbit device calculate distance?

Fitbit devices calculate distance by multiplying your walking steps by your walking stride length and multiplying your running steps by your running stride length. We estimate your stride lengths using your height and sex. If your Fitbit device uses GPS and you track 1 or more runs using on-board or connected GPS, we evaluate that data to automatically update your running stride length. For best results, run at a comfortable pace for at least 10 minutes.

If you prefer to measure your walking and running stride lengths yourself and enter them manually, see How do I measure and adjust my stride length?

Note that when you're tracking an activity with GPS, Fitbit calculates your distance using GPS data rather than steps. If you begin moving before you get a GPS signal, the tracker will calculate distance using steps and stride length as described above until a GPS signal is found.

How does my Fitbit device calculate calories burned?

Fitbit devices estimate your calorie burn based on your age, sex, height, and weight. If your device measures heart rate, the calorie burn estimate also takes heart rate into account. Note that the value you see on your Fitbit device when you wake up in the morning is your estimated calorie burn for the day so far. You still burn calories even if you are sedentary or sleeping.

Note that in certain regions, you see kilojoules instead of calories in the Fitbit app. To change your units of measurement, see How do I change the units of measurement on my Fitbit device?

When does the data on my Fitbit device reset?

Your Fitbit device resets your data to zero each night at midnight. For most devices, your minute-to-minute data is stored in your tracker for up to 7 days without syncing. If you have a Fitbit Alta your minute-to-minute data is stored for up to 5 days. A daily summary of your activity is stored for up to 30 days.
Last updated: July 12, 2019
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