How Does Fitbit Calculate Calories Burned?

Your BMR explained

The Fitbit calorie burner tracker feature can be useful for when planning a diet or workout schedule and, much like the step tracking, can provide insight into how much or how little you’re moving each day and if you’re consuming more calories than you’re burning. Here's how Fitbit calculates calories burned.

How Does Fitbit Calculate Calories?

The Fitbit calories burned stats are calculated by a using a variety of data provided by you, the user, and information collected by the Fitbit trackers themselves.

The option to view kilojoules instead of calories can be enabled in all Fitbit devices and apps. Simply tap your profile image, then tap Advanced Settings > Units.

Here’s what Fitbit uses to measure your daily calorie burn.

Basal Metabolic Rate (BMR)

Your BMR, or basal metabolic rate, is an estimate of how much energy your body uses while at rest or when not performing any extraneous activity such as playing sports or running. Fitbit works out a rough estimate of your BMR by using the personal data you provided when filling out your profile such as your height, gender, weight, and age.

If you use a Fitbit Aria smart scale, your current weight will be automatically synced to your Fitbit profile each time you weigh yourself so you won’t have to manually change it if you gain or lose weight.

This BMR information is why your Fitbit app will show you burning calories even when you haven’t done any exercise and have just been lounging around watching Netflix or Disney+ all day. Your body is burning calories all of the time.

Calories Burned screen in the Windows 10 Fitbit app.

Other information often used to determine a person’s BMR are breathing rate, blood pressure, and heart rate.

Heart Rate

While Fitbit devices can’t measure your breathing rate and blood pressure, most Fitbit trackers that can be worn on your wrist can measure your heart rate and will sync this data to your account to improve the calorie burn estimate. Generally, a higher heart rate means a faster metabolism while a slower heart rate implies that you’re burning calories at a slower rate.

Some examples of Fitbit trackers that can measure your heart rate include the Fitbit Ionic, Fitbit Blaze, Fitbit Versa, Fitbit Versa 2, Fitbit Charge 2, Fitbit Charge 3, and the Fitbit Inspire HR.

Daily Steps

All Fitbit trackers can record how many steps you take each day. Not only is this technology used to measure when you’re active but it’s also good for detecting how much you don’t move. Fitbit uses this information, and other data, to help guestimate how many calories you burn.

Tracked Exercises

When you log an activity in the Fitbit app, Fitbit will estimate a level of calorie burn based on the type of activity completed and how long you were doing it for. This number will be added to your daily total.

Logging exercises in the Fitbit apps can often cause a higher rate of calorie burn than what actually occurred as your profile will log both the BMR burn and the estimated exercise-related burn for that same time period. Any steps made during the exercise can also inflate the total number of calories burned.

What About Fitbit Calorie Counter Features?

The Fitbit apps on iOS, Android, and Windows all contain a calorie counting feature that lets you manually log foods that you consume throughout the day. This feature combines with the calorie burned Fitbit feature and shows you how many calories you’re consuming versus how many you’ve burnt throughout the day.

To add Fitbit calorie counting to your app dashboard, tap Discover > Health & Fitness Stats > Food > Add to Today.

Fitbit iOS app.