Swimming has the widest range of any activity here. A relaxed backstroke is closer to a walk, while butterfly is one of the most demanding exercises measured. Recreational and training versions of the same stroke differ by about double, so be honest about the effort.
Why swimming estimates vary so much
Technique makes a big difference. A skilled swimmer moves through the water efficiently and may burn less at a given speed than a beginner working hard to stay level. Water temperature and rest between lengths also matter. If you stop at the wall for long breaks, count only your swimming time.
Total vs net calories
Your body burns calories all day just to keep running, roughly 1 MET. The total figure includes those calories. The net figure subtracts them, leaving only the extra energy the activity cost. Net is the more honest number if you are thinking about how much a workout adds to a calorie deficit.
Don't count the same calories twice
If you set a calorie target with our TDEE calculator and chose an activity level that includes your usual workouts, those workouts are already in your target. Adding exercise calories on top would count them twice. Use these numbers for workouts beyond your normal routine, or to compare activities.
How accurate is this?
MET values are averages measured in groups of adults aged 19 to 59. Your real burn can differ by 10 to 20% or more because of fitness, technique, body composition and how hard you actually worked. Adults over 60 often burn somewhat less than these estimates; a separate Compendium for older adults exists for that reason. Treat the result as a solid estimate rather than an exact count. Fitness trackers are no more precise; see how accurate fitness trackers are for calories.
Questions people ask
How many calories does swimming for 30 minutes burn?
For a 155 lb person, slow recreational freestyle burns about 215 calories in total, while fast freestyle is closer to 360. The table on this page covers other strokes and weights.
Which swimming stroke burns the most calories?
Butterfly, rated about 13.8 METs. Among strokes most people can keep up for a while, fast freestyle and training-pace breaststroke are close behind.
Does water aerobics burn many calories?
General water aerobics is rated about 5.5 METs, similar to brisk walking, and high-intensity classes about 7.5. It is a good option when joint pain makes land exercise hard.
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. Journal of Sport and Health Science. 2024;13(1):6–12. pacompendium.com