Swimming burns less per minute
Water carries heat away about 25 times faster than air, and you are horizontal, so swimming costs fewer calories per minute than running at a comparable effort. Moderate freestyle sits around 8.3 METs; running at 10 km/h is about 10. The trade-off is that most people can swim for longer without joint stress.
Stroke matters more than pace
Butterfly is 13.8 METs, breaststroke 10.3, freestyle 8.3 at a moderate effort. That is a 60% spread for the same time in the water. The table in the result shows what your session would cost at each stroke, which is useful when a coach swaps the set.
What the estimate misses
Technique and buoyancy change the cost substantially. A wetsuit reduces it; poor body position increases it. Water temperature also matters — cold water raises metabolic rate but shortens the session. Treat the number as a comparison between sessions rather than a precise expenditure.
Frequently Asked Questions
How many calories does swimming burn per hour?
About 500–700 kcal per hour for a 70 kg swimmer at a moderate freestyle effort, depending on pace and technique.
Is swimming better than running for weight loss?
Per minute, running burns more. Per session, it depends on how long you swim. Swimming is kinder to joints and often easier to sustain.
Does cold water burn more calories?
Slightly, because the body works to maintain temperature — but the effect is small compared with the session length.
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