Swimming works nearly every muscle group, and its energy cost depends heavily on stroke and effort. A relaxed breaststroke is a moderate 5.3 METs, while a competitive butterfly can top 13.8. Between those extremes lie freestyle laps, backstroke and treading water, each with its own value in the Compendium of Physical Activities. This calculator lets you pick the stroke and intensity that match your swim and returns gross and net calories for your weight and time in the pool.
How to use the calories burned swimming calculator
- Enter your body weight in kilograms, pounds, grams or ounces.
- Choose the stroke and effort that matches what you did. The MET value is shown beside each option.
- Enter the minutes you spent.
- Read the gross and net calories, the hourly rate and the MET used.
Stroke and effort calories formula
Net calories = (MET − 1) × weight (kg) × time (hours)
Calories per hour = MET × weight (kg)
MET values are from the 2024 Adult Compendium of Physical Activities (Herrmann et al., J Sport Health Sci 2024;13:6–12). One MET is the energy you use sitting quietly, about 1 kcal per kilogram per hour. The values below range from 3.5 METs for “treading water, moderate effort” to 13.8 METs for “butterfly, general”.
The Compendium MET values include the energy you would use at rest anyway (1 MET). The “net” figure subtracts that resting share: (MET − 1) × weight × hours. Net calories are the better figure to compare with a food diary, because your daily calorie target already includes resting energy.
Worked example
A 70 kg person does “Freestyle laps, slow, recreational” for 30 minutes (Compendium code 18240, 5.8 METs).
- Gross: 5.8 × 70 × 30 ÷ 60 = 203 kcal
- Net: (5.8 − 1) × 70 × 30 ÷ 60 = 168 kcal
- Per hour: 5.8 × 70 = 406 kcal
Calories for 30 minutes by stroke and effort and body weight
| Stroke and effort | Compendium code | MET | 60 kg | 70 kg | 80 kg | 90 kg |
|---|---|---|---|---|---|---|
| Treading water, moderate effort | 18350 | 3.5 | 105 | 122 | 140 | 158 |
| Backstroke, recreational | 18255 | 4.8 | 144 | 168 | 192 | 216 |
| Breaststroke, recreational | 18265 | 5.3 | 159 | 186 | 212 | 238 |
| Water aerobics, general | 18355 | 5.5 | 165 | 192 | 220 | 248 |
| Freestyle laps, slow, recreational | 18240 | 5.8 | 174 | 203 | 232 | 261 |
| Crawl, slow, 30–45 yd/min | 18292 | 5.8 | 174 | 203 | 232 | 261 |
| Crawl, medium speed, ~50 yd/min | 18290 | 8 | 240 | 280 | 320 | 360 |
| Backstroke, training or competition | 18250 | 9.5 | 285 | 332 | 380 | 428 |
| Freestyle laps, fast, vigorous | 18230 | 9.8 | 294 | 343 | 392 | 441 |
| Crawl, fast, ~75 yd/min | 18280 | 10.5 | 315 | 368 | 420 | 472 |
| Breaststroke, training or competition | 18260 | 10.3 | 309 | 360 | 412 | 464 |
| Butterfly, general | 18270 | 13.8 | 414 | 483 | 552 | 621 |
Stroke, speed and efficiency
In the water, energy cost rises steeply with speed because drag grows with the square of velocity. That is why the Compendium rates freestyle at 5.8 METs for a slow recreational swim, 8.0 METs at about 50 yards a minute, 10.5 METs at about 75 yards a minute and 14.5 METs for elite competition speeds. Swimmers differ widely in technique, so two people of the same weight can burn very different amounts at the same pace: an efficient swimmer uses less energy to go the same distance. Butterfly is the most demanding stroke at 13.8 METs, while recreational backstroke at 4.8 is among the lightest.
Cool water also raises the energy cost of staying warm, but the effect is small for most swims and is not included in the MET values. Time resting at the wall is not swimming time; count only time in motion.
Getting more from your sessions
- Match the stroke. Use the closest option if you mix strokes, or split the session by stroke.
- Count moving time. Rests between sets reduce the average.
- Use yards per minute if you know your pace. The crawl options give a speed reference for 30–45, about 50 and about 75 yards a minute.
- Hydrate. You sweat in the pool even though you do not notice it.
Limits of the estimate
MET values are averages for healthy adults, so real energy use varies with fitness, technique, conditions and body composition by 10 to 20 percent or more. Compare activities with the Calories Burned Calculator and the MET Calculator, or see the Calories Burned Running Calculator and Calories Burned Cycling Calculator. To plan your daily intake use the Calorie Calculator and TDEE Calculator.
This page is for information only and is not medical advice. If you have a heart condition, joint problems, are pregnant or are new to exercise, check with a doctor before starting a programme.
Sources
- Herrmann SD, Willis EA, Ainsworth BE, et al. 2024 Adult Compendium of Physical Activities: A third update of the energy costs of human activities. J Sport Health Sci 2024;13:6–12.
- American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription, 11th edition, 2021 (metabolic calculations).
Frequently asked questions
How many calories does swimming burn in 30 minutes?
For a 70 kg person, slow recreational freestyle (5.8 METs) burns about 203 kcal in 30 minutes, medium-speed crawl (8.0 METs) about 280 kcal, and fast freestyle (9.8 METs) about 343 kcal.
Which stroke burns the most calories?
Butterfly (13.8 METs) is the most demanding, followed by competitive breaststroke (10.3), fast freestyle (9.8) and training backstroke (9.5). Recreational breaststroke and backstroke are much gentler.
Is swimming good for weight loss?
It burns a lot of energy and is gentle on the joints, which suits many people. As with all exercise, weight change depends on total energy balance, and some swimmers find that water exercise increases appetite.
Why do I burn fewer calories than the calculator says?
The Compendium values assume continuous swimming at the stated effort. Rests, kickboard drills and slow warm-up laps lower the average, so choose a lower intensity or count only active minutes.