Calories Burned Calculator: How Many Calories Does Exercise Burn?

Callie is our app. The calculator on this page works without it.

Pick an activity, enter your weight and the minutes you did it, and the calculator estimates the calories you burned using the published MET value for that activity.

The 30-second answer

Calories burned ≈ MET × body weight (kg) × time (hours). The MET is how hard the activity is compared with sitting still, taken from the 2024 Adult Compendium of Physical Activities. A 70 kg (154 lb) person burns about 168 kcal on a 30-minute brisk walk and about 326 kcal on a 30-minute run at 6 mph. Expect your real number to be within about 20–30% of the estimate, and expect your watch to disagree with it.

Calories burned per 30 minutes, by activity

MET values are from the 2024 Adult Compendium (Herrmann et al., 2024). Calories are gross: they include the roughly 35 kcal (70 kg) or 45 kcal (90 kg) you would burn sitting for half an hour.

Two patterns stand out. A heavier body burns more doing the same thing, in direct proportion to weight. And the gap between a walk and a run is smaller than it feels: a brisk walk burns a little over half of what a 6 mph run does in the same time, so walking for twice as long gets you close.

What a MET is, and why it's only a starting point

A MET (metabolic equivalent of task) compares an activity with sitting quietly. By convention, 1 MET is 1 kcal per kilogram per hour, or 3.5 ml of oxygen per kilogram per minute. An activity rated 6 METs uses about six times the energy of rest. The Compendium, first published in 1993, lists MET values for activities from studies that measured people's oxygen use while they did them. The 2024 edition covers 1,114 activities for adults aged 19 to 59: 912 with measured values and 202 estimated. It added 303 activities, changed 176 existing values, and moved older adults and wheelchair users into separate compendia.

The convention has a known weakness. The 3.5 ml/kg/min figure came from one 70 kg, 40-year-old man. When Byrne and colleagues measured resting metabolism in 769 adults, the average was 2.6 ml/kg/min, and the standard MET overestimated resting energy expenditure by about 20%. Body composition explained most of the difference. People with more body fat burn less per kilogram at rest than the formula assumes, so MET-based exercise estimates tend to run high for them too.

Fitness, technique, terrain, wind and heat all move the real number too. A trained runner is more economical than a beginner at the same pace. That is why the calculator shows a range of ±20–30% in its note rather than claiming precision.

Gross versus net. MET × kg × hours gives the total you burned during the session, including what you'd have burned on the sofa. The extra calories from exercising are about (MET − 1) × kg × hours. For a 30-minute brisk walk at 70 kg that's 133 kcal extra rather than 168. The calculator shows both.

Why fitness trackers get calorie burn wrong

Wrist devices measure heart rate well and calorie burn poorly. They estimate energy from heart rate, movement and your profile, with each company's own model.

• Stanford, 2017. Shcherbina et al. tested seven wrist devices (Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn, Samsung Gear S2) on 60 adults against lab indirect calorimetry while sitting, walking, running and cycling. Six devices had heart-rate error under 5% on the bike. For energy expenditure, no device got under 20% error, and median errors ranged from 27% for the best device to 93% for the worst. Error was higher for walking, for people with a higher BMI, for men and for darker skin tones.
• Shanghai, 2022. Le et al. had 20 adults walk at 6 km/h and run at 10 km/h for 2 km. The Apple Watch Series 6 and Garmin Fenix 6 both reported significantly more energy than the reference gas analyser for walking and running. The Huawei Watch GT 2e did not. Running errors were 24.4%, 21.8% and 11.9%.
• Meta-analysis, 2020. A review of 60 validation studies in the British Journal of Sports Medicine found accuracy varied widely by device and activity, and that combining heart rate with movement sensors reduced the error.

Devices from the same brand can also change between models and software updates, so a test of an older watch says little about yours.

The practical upshot: use your watch's calorie number to compare your own workouts with each other, not as a precise figure to eat against.

Should you eat back exercise calories?

It depends on how your calorie target was set.

• If your target assumes a sedentary day (many apps do this when you pick "sedentary"), your exercise is not in it yet. On days you exercise, eating back some of it keeps your deficit where you planned it. A common rule of thumb is to eat back about half, to allow for overestimates.
• If your target already includes an activity level (you chose "moderately active" in a TDEE calculator), your usual training is already counted. Adding the watch's number on top counts it twice. This is a common reason a calorie deficit stops working.

There's a second reason to be careful. Studies of total daily energy expenditure using doubly labelled water suggest the body partly compensates when activity goes up. Pontzer et al. (2016) measured 332 adults in five countries: total energy expenditure rose with activity at lower levels, then levelled off at higher ones. Exercise still matters for health, mood and keeping muscle while you lose fat, but its calorie effect is often smaller than the session total suggests.

The reliable test is your weight trend. Pick an approach, follow it for 2–4 weeks, and adjust your intake if the trend doesn't match what you expected. Our guide to how many calories to eat to lose weight walks through setting the starting target.

How Callie fits in

Callie: AI Calorie Tracker syncs with Apple Health on iPhone and Health Connect on Android, where many watches and fitness apps write workout data. It also re-tunes your calorie target every two weeks from your actual weight trend. That second part matters here: if your watch or a MET estimate is consistently off, the target follows what your weight is doing rather than what the device claimed. Our Apple Health calorie tracker comparison covers how other apps handle watch calories, including ones that ignore them on purpose.

When a different tool is the better choice

• For one person's real burn on one activity, a lab test with a gas analyser (indirect calorimetry) beats any formula. Some sports science labs and universities offer them.
• For comparing your own sessions over time, a heart-rate chest strap paired with your watch is more consistent than wrist-only estimates.
• For older adults or wheelchair users, the Compendium publishes separate Older Adult and Wheelchair compendia with values measured in those groups. This calculator uses the adult values, which cover ages 19 to 59.
• For daily total burn rather than one workout, use a TDEE calculator and then check it against your weight trend.

Sources

1. Herrmann SD, Willis EA, Ainsworth BE, et al. 2024 Adult Compendium of Physical Activities: A third update of the energy costs of human activities. Journal of Sport and Health Science, 2024;13(1):6–12. https://doi.org/10.1016/j.jshs.2023.10.010 (MET values checked at https://pacompendium.com/, accessed 2026-10-09)
2. Shcherbina A, Mattsson CM, Waggott D, et al. Accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure in a diverse cohort. Journal of Personalized Medicine, 2017;7(2):3. https://pubmed.ncbi.nlm.nih.gov/28538708/ (accessed 2026-10-09)
3. Le S, Wang X, Zhang T, et al. Validity of three smartwatches in estimating energy expenditure during outdoor walking and running. Frontiers in Physiology, 2022;13:995575. https://pubmed.ncbi.nlm.nih.gov/36225296/ (accessed 2026-10-09)
4. O'Driscoll R, Turicchi J, Beaulieu K, et al. How well do activity monitors estimate energy expenditure? A systematic review and meta-analysis of the validity of current technologies. British Journal of Sports Medicine, 2020;54(6):332–340. https://pubmed.ncbi.nlm.nih.gov/30194221/ (accessed 2026-10-09)
5. Byrne NM, Hills AP, Hunter GR, et al. Metabolic equivalent: one size does not fit all. Journal of Applied Physiology, 2005;99(3):1112–1119. https://pubmed.ncbi.nlm.nih.gov/15831804/ (accessed 2026-10-09)
6. Pontzer H, Durazo-Arvizu R, Dugas LR, et al. Constrained total energy expenditure and metabolic adaptation to physical activity in adult humans. Current Biology, 2016;26(3):410–417. https://pubmed.ncbi.nlm.nih.gov/26832439/ (accessed 2026-10-09)