What's My TDEE

How accurate are your watch’s calories?

Put in a workout and what your watch said it burned. You’ll see how it compares with the published average for that activity at your weight, and what the research says about watch accuracy.

Updated

Sex
Height
Weight
What that number counts

Your watch

For 30 minutes of running (10 min/mile) at 65 kg, with your watch showing 300 active kcal:

+8%against the estimate

Your watch says 300 kcal. The Compendium’s published average for this activity, scaled to your weight, puts it at about 280 extra kcal. That’s within 10%, as close as either figure can be relied on.

Neither number is a measurement: both are estimates from your size and movement.

Watch calories: the key numbers

  • Even recent wrist trackers are about 10% to 40% out on calories against lab measurement, while step counts on steady walks are usually within 5% (Hogue, 2026, 47 studies).
  • Apple Watch calorie error was “inconsistent and frequently large” in the newest review of its accuracy (Lambe, 2026, 82 studies).
  • Across 24 reviews, wearables’ calorie figures ranged from about 21% too low to 15% too high, so there’s no fixed correction (Doherty, 2024).
  • Fitbits tend to come in low on calories (Chevance, 2022).
  • Apple’s Active Calories leave out resting burn; Fitbit’s calories burned include it. Only an active figure compares with exercise calories.

What reviews have found

What six reviews found about the accuracy of watch and tracker calories
ReviewCoveredCalories
Lambe et al., 2026Apple Watch, 82 studiesCalorie error “inconsistent and frequently large”; steps and sleep moderately accurate.
Hogue et al., 2026Wrist trackers, 47 studiesEven recent devices 10% to 40% out on calories; steps usually within 5% on steady walks.
Choe and Kang, 2025Apple Watch, 56 studiesEvery calorie subgroup outside the 10% error usually accepted as valid.
Doherty et al., 2024All consumer wearables, 24 reviewsAverage 3% low, but from about 21% too low to 15% too high. Only about 1 device in 9 validated for anything.
Chevance et al., 2022FitbitCalories underestimated, by about 2.8 kcal a minute on average.
Fuller et al., 2020Commercial wearables, 158 publications“For energy expenditure, no brand was accurate.”

The estimate here uses the activity’s cost per kg from the 2024 Compendium of Physical Activities, with your own resting rate for total calories. It’s an average for people your size, not a measurement either, so treat a small gap as agreement.

Short answers

How accurate are Apple Watch calories?

Less accurate than its step count. The newest review of Apple Watch accuracy (2026, 82 studies) found its calorie error “inconsistent and frequently large”, while steps and sleep were moderately accurate. A 2025 meta-analysis found every calorie subgroup outside the 10% error usually accepted as valid.

Does my watch show active or total calories?

It depends on the brand. Apple counts Active Calories, the Move ring, as “calories burned above basal (resting) calories”, and adds resting calories to make the total. Fitbit’s calories burned are your total for the day, including your basal rate, and even its activity calories include it. Only an active figure compares with the extra calories here.

Do fitness trackers overestimate calories?

Not always: the errors go both ways. Across 24 reviews, wearables ranged from about 21% too low to 15% too high (Doherty, 2024), and Fitbits tend to come in low (Chevance, 2022). So there’s no fixed correction to apply to your watch.

Should I eat back the calories my watch says I burned?

Only the active calories from workouts, and not all of them. On average the body offsets about 28% of exercise calories (Careau, 2021), and the watch’s own figure may be well out. Adding the workout to the TDEE calculator counts it at 72 to 100% of the Compendium’s figure instead.

Sources

Checked against each source on 22 and 23 October 2026

  • Lambe R, et al. (2026). The accuracy of Apple Watch measurements: a living systematic review and meta-analysis. NPJ Digit Med 9(1):63. PMID 41513748
  • Hogue T, et al. (2026). Advancement in wrist worn physical activity trackers: technological developments and measurement accuracy: a systematic review. Front Digit Health 8:1820224. PMID 42698643
  • Choe JP, Kang M (2025). Apple watch accuracy in monitoring health metrics: a systematic review and meta-analysis. Physiol Meas 46(4). PMID 40199339
  • Doherty C, et al. (2024). Keeping pace with wearables: a living umbrella review of systematic reviews evaluating the accuracy of consumer wearable technologies in health measurement. Sports Med 54(11):2907–26. PMID 39080098
  • Chevance G, et al. (2022). Accuracy and precision of energy expenditure, heart rate, and steps measured by combined-sensing Fitbits against reference measures: systematic review and meta-analysis. JMIR Mhealth Uhealth 10(4):e35626. PMID 35416777
  • Fuller D, et al. (2020). Reliability and validity of commercially available wearable devices for measuring steps, energy expenditure, and heart rate: systematic review. JMIR Mhealth Uhealth 8(9):e18694. PMID 32897239
  • Apple (2024). Using Apple Watch to measure heart rate, calorimetry, and activity. apple.com
  • Apple Developer Documentation. activeEnergyBurned (HealthKit). developer.apple.com
  • Google Health Help. How does my Fitbit device calculate my daily activity? support.google.com
  • Fitbit Web API Reference. Get Daily Activity Summary. dev.fitbit.com
  • Herrmann SD, et al. (2024). 2024 Adult Compendium of Physical Activities: a third update of the energy costs of human activities. J Sport Health Sci 13(1):6–12. PMID 38242596
  • Careau V, et al. (2021). Energy compensation and adiposity in humans. Curr Biol 31(20):4659–66. PMID 34453886
  • Mifflin MD, St Jeor ST, et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 51(2):241–7. PMID 2305711