How Does Fitbit Calculate Calories Burned

Fitbit has evolved into more than just a wearable device; it’s a comprehensive health and fitness companion. One of its most useful features is the calorie tracker, which serves as a cornerstone for anyone planning a meticulous diet or a well-structured workout schedule.

This feature goes beyond merely counting calories or kilojoules. It offers a holistic view of your energy expenditure, helping you make informed decisions about your health and lifestyle.

By simply tapping on your profile image and navigating to the ‘Advanced Settings,’ you can customize the units to your preference, switching between calories and kilojoules as needed.

This level of customization and detail makes Fitbit a versatile tool, adaptable to various fitness goals and nutritional plans.

Whether you’re a fitness enthusiast or someone just starting on the path to a healthier lifestyle, understanding how Fitbit calculates calories burned can provide valuable insights into your daily routines.


How Does Fitbit Calculate Calories Burned

Fitbit employs a multi-faceted approach to estimate the number of calories you burn throughout the day. It starts with your Basal Metabolic Rate (BMR), which is the rate at which your body burns calories at rest to maintain essential functions like breathing, blood circulation, and heartbeat. Your BMR accounts for about half of your daily calorie burn, even when you’re asleep or not moving.

Fitbit combines this with physical data you’ve entered into your account, such as age, weight, height, and sex. The device also collects activity data, especially during exercise, to provide a more accurate estimate. Your heart rate data is a crucial part of this calculation. So, if you ever wonder, “How do I see the change in units of measurement or the information collected daily?” you can simply tap into the tracker’s settings and explore.How Does Fitbit Calculate Calories Burned

Basal Metabolic Rate (BMR):

Your BMR is essentially the energy your body needs to function while at rest, without any extraneous activities like sports or running.

Fitbit estimates your BMR using personal data you’ve entered into your profile, such as your age, weight, height, and gender. Even when you’re lounging around watching Netflix or Disney+, your body is still burning calories.

If you own a Fitbit Aria smart scale, your current weight will be automatically synced to your profile, eliminating the need to manually update it whenever you gain or lose weight.

Heart Rate:

Fitbit devices like the Fitbit Ionic, Fitbit Blaze, Fitbit Versa, Fitbit Versa 2, Fitbit Charge 2, Fitbit Charge 3, and Fitbit Inspire HR come equipped with heart rate monitors. These devices sync your heart rate data to your account, providing a more accurate estimate of your calorie burn.

While Fitbit can’t measure your breathing rate or blood pressure, the heart rate data is a significant factor in calculating your metabolism rate.

Daily Steps:

Fitbit trackers are equipped with technology that not only detects when you’re active but also when you’re not moving much. The number of steps you take each day is another crucial data point that Fitbit uses to estimate your daily calorie burn.

Tracked Exercises:

When you log activities in the Fitbit app, it estimates the calories burned based on the type of activity and its duration. This data is then added to your daily total.

It’s worth noting that logging exercises can inflate the total number of calories burned, as the app combines your BMR burn with the estimated exercise-related burn for the same time period.

What Factors Can Affect the Accuracy of Fitbit’s Calorie Burn Counter?

Before diving into the intricacies of how Fitbit calculates calorie burn, it’s essential to understand that the number of calories an individual burns depends on several factors.

Fitbit’s calorie counter accuracy is influenced by a few of these factors. Let’s explore some of the primary elements that can affect the accuracy of Fitbit’s calorie burn estimates.

Heart Rate Variability:

Everyone’s heart rate varies to a certain degree. While Fitbit strives to provide accurate readings, there are instances where some people might not get a precise heart rate measurement.

This variability can lead to inaccurate calorie burn estimates, impacting the overall tracking of one’s fitness journey. It’s crucial to remember that while heart rate is a significant factor, it’s not the only one that determines calorie burn.

Wrist Placement:

Fitbit devices are specifically designed to be worn on the non-dominant wrist. Proper positioning is crucial for obtaining an accurate heart rate reading. If the Fitbit tracker isn’t positioned correctly, about two to three fingers away from the wrist bone, it might not capture a good heart rate reading.

This misplacement can subsequently lead to an inaccurate calorie burn estimate, emphasizing the importance of wearing the device correctly.

Activity Intensity:

The intensity of activities plays a pivotal role in calorie burn estimates. More intense activities might cause Fitbit devices to overestimate energy expenditure, depending on how and where you wear the device.

Conversely, low-intensity activities, like walking, can also influence the calorie burn estimate. A study from the Journal of Personal Medicine highlighted that fitness trackers, including Fitbit, had the highest level of error when tracking walking compared to other activities.

Overall Activity Level:

The accuracy of Fitbit’s calorie burn estimate is most pronounced when an individual engages in moderate to vigorous activities regularly. For those who are exceptionally active, Fitbit might overestimate the calorie burn.

On the other hand, if one leads a sedentary lifestyle, the device might underestimate the calorie burn. It’s a balancing act, and understanding one’s activity level can provide more context to the readings.


Weight plays a significant role in how Fitbit devices calculate calories burned. The device’s estimate might be less accurate for individuals who don’t fall within a specific weight range.

It’s essential to keep the Fitbit profile updated with the most recent weight to ensure the most accurate calorie burn calculations. After all, the device uses this weight data, among other factors, to provide a comprehensive view of one’s calorie expenditure.

How Accurate Is the Fitbit Calorie Burn Counter?

In 2019, a BBC article shed light on a study that scrutinized the accuracy of the Fitbit Charge 2’s calorie burn counter. The findings were intriguing. When participants were running, the device underestimated the calories burned by about 4 percent.

Conversely, when participants were walking, the calorie burn estimation soared to an overestimation of 50 percent. This discrepancy in accuracy suggests that while Fitbit is a reliable tool, it’s essential to consider various factors that might influence its readings. Interestingly, the study also highlighted that higher-priced trackers exhibited more accurate results.

The Fitbit calorie burn counter’s accuracy is influenced by several factors. While it’s a widely recognized tool for tracking physical activity, it’s crucial to understand that no device is infallible.

The study’s findings underscore the importance of using Fitbit as a guide rather than an absolute measure.

It’s always beneficial to cross-reference with other methods or be aware of potential discrepancies, especially when the readings can vary significantly between activities like running and walking.

Fitbit Calories Burned Accuracy by Model:

Every Fitbit model is crafted uniquely, leading to slight variations in the accuracy of their calorie burn counters. The newer and pricier models, like the Fitbit Charge 4, have been lauded for their precision.

A study by Wareable reinforced this claim, finding the Charge 4 to be one of the most accurate fitness trackers available, especially in tracking heart rate and steps. Following its legacy, the upgraded Fitbit Charge 5 further enhanced its accuracy.

On the flip side, the Fitbit Inspire 2, although a commendable device, has a marginally less accurate calorie burn counter. However, it’s essential to note that its readings are still within an acceptable range.

The Inspire 2, being an entry-level model without GPS, might not match the accuracy levels of its more expensive counterparts like the Charge or Sense.

But with the introduction of the Fitbit Inspire 3 and its significant improvements, one might consider investing in the newer model for enhanced accuracy.

Making the most out of your fitness tracker:

To truly harness the power of a fitness tracker, one must have a comprehensive understanding of its limitations.

No device is perfect, and each comes with its unique set of strengths and weaknesses. By recognizing these nuances, users can make informed decisions and choose the best model tailored to their needs.

Whether you’re a fitness enthusiast or someone just starting their journey, it’s essential to be well-informed and choose a model that aligns with your goals. After all, the right fitness tracker not only monitors your progress but also motivates you to push your boundaries.

How to Improve the Accuracy of the Fitbit Calorie Burn Counter؟

Wear it on your non-dominant wrist:

The company behind Fitbit has designed these devices with precision in mind, especially when it comes to heart rate readings. To get the most accurate data, it’s advisable to wear your Fitbit on your non-dominant wrist.

The company’s app even offers an option to specify which hand you’re using, whether it’s your dominant or non-dominant hand. By doing so, you’re aligning with the company’s expectations and ensuring that the device can calculate your calorie burn as accurately as possible.

Keep it snug:

The fit of your Fitbit on your wrist plays a crucial role in the accuracy of heart rate readings, which in turn affects the calorie burn estimate.

The device should be snug but not overly tight. If it’s too loose, the device may struggle to get a reliable heart rate reading, leading to less accurate data. So, make sure it’s snug enough to stay in place but not so tight that it’s uncomfortable.

Update your weight:

Your current weight is a key factor that Fitbit uses to calculate the calories you’ve burned. Therefore, it’s essential to keep your weight information up-to-date in the Fitbit app.

An outdated weight can lead to miscalculations in the number of calories burned, making your fitness tracking less reliable. Regularly updating this information ensures that your Fitbit can make a more accurate estimate.

Be active:

Fitbit devices are most accurate when tracking moderate to vigorous activities. If you’re leading an active lifestyle, the device’s calorie burn estimates are likely to be more accurate. So, to get the most out of your Fitbit, make sure you’re engaging in a good mix of moderate and vigorous activities.

The more you move, the better your Fitbit can estimate your calorie burn, making your fitness journey more effective and informed.

What if My Fitbit Says I’m Burning More Calories Than I Actually Am?

The Concern Over Calorie Overestimation:

If your Fitbit tracker is indicating that you’re burning more calories than you think you are, don’t fret. It’s essential to remember that the calorie count is an estimate and not 100 percent accurate.

Factors like being highly active can lead to the tracker overestimating your calorie burn, especially if your heart rate is frequently elevated.

The Science and Solutions Behind Discrepancies:

Research published in Biomedical Optics Express suggests that the sensors in Fitbit devices may not be as precise for individuals who are sedentary or obese. If you notice significant discrepancies between your Fitbit’s calorie count and other forms of measurement, consider factory resetting your device. Make sure it syncs properly to track your activity level more accurately.

How to Use the Fitbit Calorie Counter?

Navigating the Fitbit App:

Fitbit offers apps for iOS, Android, and Windows platforms, each featuring a calorie-counting tool. To manually log the food you’ve consumed, navigate to the dashboard and go to “Discover” > “Health & Fitness Stats” > “Food” > “Add to Today.”

Combining Caloric Intake and Output:

The Fitbit app not only allows you to log the food you’ve eaten but also combines this data with the calories you’ve burnt. This comprehensive feature provides a holistic view of your caloric balance for the day, helping you make informed decisions about your health.

Does Fitbit Provide an Accurate Calorie Burn Estimate?

The General Accuracy of Fitbit Trackers:

The question of Fitbit’s calorie burn accuracy is a valid one. Generally, Fitbit trackers are accurate within a few percentage points. They serve as good motivational tools that can inspire progress and provide a reasonable idea of your caloric burn, aligning closely with your fitness goals.

Factors Affecting Calorie Burn Estimates:

The model of the Fitbit you use can influence the accuracy of the calorie burn estimate. While no tracker can guarantee 100 percent accuracy, Fitbit devices are among the more reliable options on the market.

They include various statistics to give you a well-rounded view of your health, including estimated calories burned.

Limitations of Fitbit’s Calorie Burn Calculation:

Fitbit devices, while advanced, have certain limitations when it comes to calorie burn calculation. The algorithm used to determine calorie burn is not always accurate.

Factors such as heart rate, weight, age, and gender are taken into account, but there are still challenges in ensuring complete accuracy.

Inaccurate Heart Rate Monitoring:

Fitbit’s calorie burn calculation is heavily dependent on accurate heart rate monitoring. However, several factors can lead to inaccurate readings. For instance, poor device placement on the wrist can result in incorrect heart rate data.

Additionally, when the device’s battery is low, it might not capture heart rate as effectively. Such inaccuracies in heart rate monitoring can subsequently affect the calorie burn calculation, making it less reliable.

Limited Activity Tracking:

The calorie burn calculation on a Fitbit device is based on the activities it can track. However, not all activities are tracked accurately.

For example, activities like weightlifting and swimming might not be measured as precisely as walking or running. This limitation can lead to inaccurate calorie burn estimates, especially if the user engages in a variety of exercises.

Individual Variations:

Fitbit’s algorithm does take into account factors such as age, gender, weight, and height. However, individual variations like genetics and specific health conditions can influence calorie burn.

The device might not always account for these unique factors, which can impact the accuracy of the calorie burn calculation.

Remember, while Fitbit offers a comprehensive overview of one’s fitness metrics, it’s essential to understand its limitations and use the data as a guideline rather than an absolute measure.

Frequently Asked Questions (FAQ):

How does Fitbit calculate the number of calories burned?

The Algorithmic Brain Behind Fitbit:

Fitbit employs a proprietary algorithm to estimate the calories you’ve burned. This algorithm is a complex blend of various factors including your age, gender, weight, and height. The aim is to provide a personalized snapshot of your caloric expenditure.

Activity Level: The X-Factor:

Your activity level throughout the day is another crucial element in Fitbit’s calorie calculation. The device uses sensors like accelerometers and gyroscopes to track your movements, whether you’re walking, running, or climbing stairs, and incorporates this data into its calorie burn estimates.

Does Fitbit calculate calories burned accurately?

The Reliability Quotient:

Fitbit’s calorie burn calculations are generally considered accurate, but they do have limitations. The algorithm can sometimes be thrown off by factors like inaccurate heart rate monitoring, leading to less-than-perfect results.

Individual Variability and Accuracy:

The accuracy of Fitbit’s calorie burn calculation can also be influenced by individual variations. These can range from genetics to health conditions, and they can affect how closely the device’s estimates align with your actual calorie burn.

How does Fitbit track activity levels?

Sensory Intelligence:

Fitbit devices are equipped with sensors like accelerometers and gyroscopes to monitor your activity level throughout the day. These sensors collect data on various activities, including walking, running, and climbing stairs, to help calculate your calorie burn.

The Data Symphony:

The data collected by Fitbit’s sensors is then synthesized to provide a comprehensive view of your day’s activities. This information is crucial for calculating the calories you’ve burned during various activities.

Can Fitbit track all types of activities accurately?

The Scope of Activity Tracking:

Fitbit’s calorie burn calculations are generally accurate for a range of activities. However, some activities like weightlifting and swimming may not be tracked as accurately, leading to potential discrepancies in the calorie burn estimates.

The Accuracy Spectrum:

The device’s ability to accurately track different types of activities can vary. While it excels in tracking common activities, it may falter when it comes to more specialized exercises, leading to inaccurate calorie burn calculations.

Can I manually log my workouts on Fitbit?

Manual Logging: A User’s Choice:

Yes, Fitbit allows you to log your workouts manually. By doing so, the device can calculate the calories burned during the activity with a higher degree of accuracy.

The Calculation Game:

When you manually log a workout, Fitbit uses this data to fine-tune its calorie burn estimates. This can be particularly useful for activities that the device might not track as accurately by default.

Can individual variations affect the accuracy of Fitbit’s calorie burn calculation?

The Genetic and Health Factors:

Individual variations, such as genetics and existing health conditions, can indeed impact the accuracy of Fitbit’s calorie burn calculations. These personal factors can either inflate or deflate the estimated number of calories burned.

The Accuracy Conundrum:

Understanding that individual variations can affect Fitbit’s calculations is crucial for interpreting the data. While the device provides a good general estimate, it may not be 100% accurate for every individual.

Can Fitbit calculate the number of calories burned during sleep?

The Nighttime Caloric Burn:

Fitbit can estimate the number of calories you burn while sleeping. This is calculated based on your Basal Metabolic Rate (BMR), which is the rate at which you burn calories while at rest.

Sleep and BMR: The Connection:

Even when you’re asleep, your body is burning calories to maintain basic functions. Fitbit uses your BMR to estimate this caloric expenditure, providing a more complete picture of your daily calorie burn.

Wrapping Up:

This article aimed to demystify the complex algorithms and data points that Fitbit uses to calculate the number of calories you burn throughout the day. From understanding your Basal Metabolic Rate to tracking your heart rate and daily steps, Fitbit offers a multi-dimensional view of your health. If you have additional questions or need further clarification, don’t hesitate to use the comment box below.

Your Fitbit device and the accompanying app serve as more than just trackers; they are your partners in your health journey. Whether you’re troubleshooting issues, like needing to factory reset your Fitbit smartwatch, or looking to sync it with your mobile device, the Fitbit App is your centralized hub for all your health data. Remember, the journey to a healthier you is a marathon, not a sprint, and every bit of data helps you better understand your body and tailor your lifestyle accordingly.

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