Question 1

How many calories does swimming burn?

Accepted Answer

For a 70 kg adult: ~580 kcal/h freestyle moderate (8.3 METs), ~720 kcal/h breaststroke vigorous (10.3 METs), ~970 kcal/h butterfly vigorous (13.8 METs). Treading water leisurely is only 245 kcal/h, but treading vigorously matches freestyle moderate at 690 kcal/h. The 2024 Compendium of Physical Activities is the canonical source for these MET tables.

Question 2

Why is butterfly so much higher than freestyle?

Accepted Answer

Butterfly engages every major muscle group simultaneously and demands continuous explosive power from the kick and pull. The arm recovery is also entirely above water, which is energetically expensive. Most adults can’t maintain butterfly past 50–100 m, so the high MET value applies only to the duration you can actually sustain it.

Question 3

Does cold water increase calorie burn?

Accepted Answer

Yes, but less than people think. Open-water swimming in 12–18 °C water adds 10–15 % to expenditure from thermoregulation (shivering thermogenesis kicks in once core temperature drops slightly). Below 10 °C the body activates brown adipose tissue, but realistically most people can’t swim long enough to capture the extra burn before hypothermia risk rises. Pool swimming at 26–28 °C has effectively no thermoregulation cost.

Question 4

Will swimming help with weight loss?

Accepted Answer

It can, but compensation effects are real: many swimmers eat 30–50 % of the burned calories back without realising it (post-pool hunger is genuinely larger than after running). Swimming is excellent for cardiovascular fitness and joint-friendly cardio in pregnancy or post-injury, but pair it with food tracking if weight loss is the goal. Swimmers also tend to be heavier than runners at the same fitness level — buoyancy and joint-protection trade off against pure mechanical efficiency.

Swimming calories calculator

How MET-based swim calculations work

Why swim coaches don’t love MET tables

Open water vs pool

Sources