How calories burned are calculated
Every estimate on this page traces back to a single research tool: the MET, or metabolic equivalent. One MET is the energy you burn sitting quietly. Walking briskly costs about 3.5 METs — three and a half times sitting still. Running costs 8 to 11. Researchers have measured these multiples for hundreds of activities and published them in the Compendium of Physical Activities, which is the reference this calculator draws on.
From there the formula is honest and simple: METs × your weight in kilograms × hours of activity. A 70 kg person running at a moderate 8.3 METs for half an hour burns 8.3 × 70 × 0.5 — about 290 calories. The same half hour of brisk walking comes to roughly 123.
Weight sits right in the middle of that formula, which explains something gym machines gloss over: a heavier person burns meaningfully more doing the same workout. The 'calories burned' readout on a treadmill that never asked your weight is decoration.
Calories burned by activity (per 30 minutes, 70 kg person)
| Activity | METs | ≈ Calories / 30 min |
|---|---|---|
| Walking, moderate pace | 3.5 | ≈ 123 |
| Weightlifting, moderate | 5.0 | ≈ 175 |
| Cycling, moderate | 6.0 | ≈ 210 |
| Swimming, moderate | 8.0 | ≈ 280 |
| Running, moderate | 8.3 | ≈ 290 |
| Soccer, competitive | 10.0 | ≈ 350 |
| Swimming, butterfly | 13.8 | ≈ 483 |
The calculator covers ten activities with multiple intensities each — these rows are a sample. Heavier than 70 kg? Your numbers are higher; lighter, lower.
Why the number is an estimate — and how far off it can be
MET values are averages taken across many measured people, and you are one specific person. Fitness level shifts things: a trained runner moves more efficiently and burns a little less at the same pace than a beginner fighting their own mechanics. Terrain, technique, rest periods between sets, even air conditioning all move the needle. Expect the true figure to sit within perhaps 10–20 percent of the estimate — good enough for planning, too coarse for bragging.
This also explains the most common dieting trap: eating back every calorie your workout supposedly burned. If the estimate ran high and the post-gym snack ran large, the deficit quietly disappears. A safer habit is to eat back half, and let your weekly weight trend tell you the rest. Your overall daily burn — exercise included — is what the TDEE calculator estimates, and the calorie calculator turns that into eating targets.
Frequently asked questions about burning calories
How are calories burned during exercise estimated?
This tool uses MET (metabolic equivalent) values from the Compendium of Physical Activities multiplied by your weight and duration.
Why do two people burn different calories doing the same workout?
Body weight, fitness level, intensity, and mechanics all change expenditure. MET values are population averages.
Should I eat back all exercise calories?
Depends on your goal. Many people eat back only part of exercise calories to avoid overestimating burn.
How do I use this calories burned calculator?
Select activity, enter weight and duration, then click Calculate.
Sources and further reading
- Ainsworth BE et al. — 2011 Compendium of Physical Activities (Med Sci Sports Exerc)
- CDC — Physical activity guidelines for adults
- American Heart Association — Physical activity recommendations
This page is for general information only and is not medical advice. Check with a doctor before starting a new exercise program, especially with existing health conditions.