Work out how many calories a swim burns from your body weight, stroke and time, using the standard MET formula, with gross and net figures shown separately.
| Input | Result |
|---|---|
| 70 kg, 30 minutes, Freestyle, moderate effort | 213 kcal gross, 176 kcal net |
| 90 kg, 60 minutes, Freestyle, moderate effort | 548 kcal gross, 454 kcal net |
| 70 kg, 30 minutes, Breaststroke, moderate effort | 195 kcal gross, 158 kcal net |
| Intensity | MET |
|---|---|
| Freestyle, moderate effort | 5.8 MET |
| Breaststroke, moderate effort | 5.3 MET |
MET values from the Compendium of Physical Activities. Only intensities reproduced consistently across independent published tables are listed here.
A MET (Metabolic Equivalent of Task) is a multiple of your resting energy use: sitting quietly is 1 MET, and an activity at 5 METs costs five times as much energy per minute as sitting still. The values published in the Compendium of Physical Activities, maintained by researchers and updated most recently in 2024, are measured averages across groups of healthy adults, rounded to the nearest 0.0, 0.3, 0.5 or 0.8.
The formula used here is the standard one from the American College of Sports Medicine:
calories per minute = MET × 3.5 × body weight (kg) ÷ 200
The 3.5 is the resting oxygen uptake in millilitres per kilogram per minute that defines 1 MET, and 200 is the conversion that turns it into kilocalories. It is the same formula most fitness trackers and cardio machines use, which is why the number here should be in the same neighbourhood as the one on your machine.
MET values are population averages, not measurements of you. Real energy cost moves with body composition, fitness, movement efficiency, terrain, water temperature and how hard you are actually working, and the 3.5 mL/kg/min constant behind the formula was derived from a single reference adult, so it fits a lean average adult far better than it fits anyone at the edges. Independent testing of consumer wearables routinely finds errors of 20–30%, in both directions.
The tool reports two figures for that reason. Gross calories is the total your body burned during the session. Net calories subtracts what you would have burned sitting down for the same length of time, that is the number that actually represents what the exercise added. If you are logging food against exercise, the net figure is the honest one.
This is an estimate, not medical advice. Nothing here diagnoses a condition, assesses a pregnancy or replaces a clinician. If you are pregnant, trying to conceive or managing a health condition, follow the guidance of your own medical team over any number a calculator produces.
A 70 kg adult swimming freestyle at moderate effort for 30 minutes burns about 213 kcal gross, or roughly 176 kcal net. Stroke matters: breaststroke at moderate effort carries a slightly lower MET value than freestyle in the published tables.
Because they are the intensities published consistently across independent MET tables. Values quoted for butterfly and for vigorous freestyle disagree between sources, so rather than print a number that would be a guess, this calculator lists only the strokes that are corroborated.
It can, and the MET tables do not capture it. Cold water adds the cost of thermoregulation, while a warm pool removes it, one more reason to read the result as an estimate rather than a measurement.
Because effort is much harder to hold steady in water. Running pace maps cleanly onto a MET value; swimming effort varies with technique, rest intervals at the wall and how streamlined you are, which is why two swimmers in the same lane can differ substantially.