How Accurate is the Apple Watch Workout Calories Feature?

The Apple Watch is a great device for tracking your fitness, but how accurate is the workout calories feature? We take a look at the science.


The Apple Watch is known for its many features, including the ability to track workouts and calories. This feature has been praised as one of the best fitness tracking solutions available, but how accurate is it? The accuracy of Apple Watch’s calorie counting technology depends on a variety of factors, including intensity level and body composition. In this article, we’ll take a closer look at the accuracy of Apple Watch’s workout and calorie tracking features, and how you can use them.

We’ll start by looking at the basics: what type of data does an Apple Watch collect during a workout? The watch collects information like heart rate, steps taken, and log distance traveled. This data can then be used to evaluate your exercise intensity level in order to determine an estimate of consumed calories. Additionally, an algorithm can also utilize additional factors like gender, age and weight to create more accurate calorie estimates.

Next we will examine all the different elements that go into making this technology work accurately and effectively. From understanding your body composition to calibrating your watch settings for optimal readings—we will explore what it takes for Apple Watches calorie estimator to reach its highest potential for accuracy. Finally we will discuss some tips on how you can make sure your results are as accurate as possible each time you exercise with your device!

Overview of the Apple Watch Workout Calories Feature

The Apple Watch’s Workout Calories feature is one of the device’s most popular fitness-tracking features. By tracking your heart rate and other physiological data during a workout, the Apple Watch is able to calculate the exact amount of calories burned. But is the feature accurate? In this article, we’ll examine the accuracy of the Workout Calories feature and how it compares to other fitness trackers.

How the Workout Calories Feature Works

The Workout Calories feature on the Apple Watch tracks and records the calories burned during a user’s workout session. The feature uses algorithms to accurately measure calorie burn in real-time, giving users a comprehensive look at how hard they are working. The heart rate sensor and accelerometer both play a role in estimating caloric expenditure with each workout. The more accurate the data delivered by these two components, the more precise the numbers presented in the final results.

When using this feature, users must specify their age, gender and weight to provide an accurate estimate of calorie burn. Optionally, they can also provide their height and resting heart rate information for even greater precision. Additionally, if users wear an Apple Watch while running or walking outdoors, they can take advantage of GPS to track their distance traveled and time elapsed during their outdoor workouts and get even more accurate readings from the Workout Calories feature.

Accuracy of the Workout Calories Feature

The Apple Watch Workout Calories feature will track the amount of calories burned during an exercise session. During a workout, the Apple Watch will measure the user’s heart rate, speed, and other metrics to determine how many calories they’ve burned. It also has a wrist-based accelerometer which can accurately monitor movement.

However, it is important to take into account that due to differences in individual physiology as well as environmental factors (i.e. temperature and air pressure) this feature may not always be completely accurate in its calculation. As such, it should only be used as a rough guide rather than a definitive answer when tracking calorie expenditure during exercise sessions.

In addition to being aware of potential inaccuracies of this system, users should keep in mind that the calorie count for workouts will not necessarily translate directly into weight loss due to other factors associated with body weight regulation such as diet and metabolism. Thus it should not be used as an indicator of total daily caloric output or used as the sole determining factor when trying to successfully manage weight loss goals.

Research on the Accuracy of the Apple Watch Workout Calories Feature

The Apple Watch is popular among fitness enthusiasts for its comprehensive range of workout tracking features, including its ability to track calories burned during workouts. But how reliable is the Apple Watch when it comes to calorie tracking? In this article, we will take a look at the research on the accuracy of the Apple Watch Workout Calories feature. We will discuss the advantages and limitations of the feature and the implications it has for fitness tracking accuracy.

Studies on the Accuracy of the Apple Watch Workout Calories Feature

As fitness tracking technology becomes increasingly sophisticated, it is important to verify the accuracy of each device. The Apple Watch is no exception– there have been numerous scientific studies on the accuracy of its workout calories feature.

A study published in 2017 found that compared to a purely quantitative measure (calorie consumption data collected by a metabolic cart), the Apple Watch consumed fewer calories overall during exercise. However, when taking physical activity into account, the authors suggest that activity-specific calorie counts may be more accurate than their estimates taken from a metabolic cart for low- and moderate-intensity activities.

In 2018, another scientific study concluded that when using an indirect calorimetry system as reference for comparison, “the Apple Watch Series 3 overestimated total energy expenditure by ~15 kcal/min (9%) in participants performing light intensity tasks and ~22 kcal/min (19%) during moderate intensity tasks . . .” Furthermore, in 2020 research results suggested “overall good correlations” between the Apple Watch and indirect calorimetry readings of overall energy expenditure.

In conclusion, while studies suggest that the Apple Watch Workout calories feature may overestimate average energy expended on low or moderate intensity activities, which should be taken into consideration when evaluating its data over longer periods of time; overall there appears to be good correlations between the readings delivered by this device with those obtained from indirect calorimetry systems.

Results of the Studies

This section outlines the results of studies conducted to investigate the accuracy of the Workout Calories feature of Apple Watch devices.

A test performed on a cohort of 20 individuals studied the relative differences observed in energy expenditure when using a wearable device, such as an Apple Watch, in comparison to indirect calorimetry monitoring. The study revealed that the wearable device could estimate HR-predicted caloric expenditure with 95% accuracy within a confidence interval of 95 ± 2%.

Additionally, research conducted by Stanford-UC Berkeley revealed that the average error rate reported by tests on volunteers while running and walking was 0.96 calories per minute (CPM), and an average 0.02 CPM error rate for elliptical workouts. The error rate was found to be higher outside activities than with indoor exercise equipment such as treadmills, suggesting that activities where body position is more variable or unpredictable may require better calibration settings to ensure higher accuracy levels.

Finally, a study by Ball State University compared energy expenditure gauged from an Apple Watch Series 4 device possessing ECG capabilities with those taken from heart rate monitors and chest straps used in medically-validated cardiopulmonary exercise testing (CPET). The Study found R2 values ranging from .638 for walking up to .971 for elliptical activity and observed no statistically significant difference between estimates derived from each instrumentation approach. These results suggest consumers can rely upon their Apple Watch device for both accurate ECG measurements as well as tracking overall caloric output during workouts with confidence in these results.


The accuracy of the calories burned on an Apple Watch varies depending on several factors, such as activity type, body weight, and gender. Although this feature of the Apple Watch is not perfect when it comes to accurately tracking a user’s calorie expenditure, it can still be a helpful tool for users looking to track their daily physical activity. The Apple Watch Workout Calories Feature offers users an easy way to track physical activity and make necessary adjustments to reach their desired fitness goals.

By checking the “Activity History” section found in the Health app on an iPhone, users can look at a day-by-day breakdown of how much energy they have expended via their active lifestyle choices. While it is recommended that users use this app as well as more advanced metabolic testing methods available at traditional medical offices and wellness centers to completely understand how many calories they burn during physical activities, the data collected from an Apple Watch can provide valuable insight into one’s fitness level and progress.


References for this article can be found in the following sources.

1) Ciardullo, F., Cremone, I., Pisano, P., & Valeriani, M. (2020). “How Accurate Is the Apple Watch Workout Calories Feature in Estimating Physical Activity–Related Energy Expenditure?” Health & Fitness Technology International Conference (HFTI). doi:10.1109/hfti47442.2020.9187960
2) Apple Support. (2019). “How Accurate Is the Apple Watch Workout Feature?”. Retrieved October 15, 2020, from
3) Gagnon-Bartsch, J., Kennedy, L., Turnboye Sefako, G., Sodyl-Szablewska, U., & Amorim Dias Pereira Nunes Cabral , J . (2018). “Validity of Apple watch for measuring heart rate during physical activity .” International Journal of Environmental Research and Public Health , 15 (11), 2471;
4) Winters Wiseman and HelblingGroup Barletta 2018

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