How this calculator works
The 2011 Compendium of Physical Activities lists swimming values from 3.5 METs for moderate treading water to 13.8 METs for butterfly. The same stroke changes with effort: recreational breaststroke is 5.3 METs while training or racing breaststroke is 10.3. The calculator applies the selected MET value to body mass and time. Water temperature matters: cold water raises energy use to maintain body heat, and warm water lowers it. Technique also matters, because an efficient swimmer covers more distance for the same effort. The estimate covers the swimming itself, not the time resting at the wall.
Formula
kcal/min = MET x 3.5 x body mass (kg) / 200. Total calories = kcal/min x minutes. Energy is shown in kcal and kJ.
Worked example
A 70 kg swimmer does 30 minutes of front crawl at medium speed: 8.3 x 3.5 x 70 / 200 = 10.17 kcal/min, or 305.0 kcal. At fast crawl the same 30 minutes gives 12.25 kcal/min and 367.5 kcal. Recreational backstroke gives 5.88 kcal/min and 176.4 kcal.
Advertisement
Frequently asked questions
Which stroke burns the most calories?
Butterfly is the most demanding at about 13.8 METs, followed by fast crawl and racing breaststroke. The best stroke for you is the one you can sustain with good technique, because a high MET value you can only hold for two minutes is not a good workout.
Does water temperature change the estimate?
Yes. Cold water increases heat loss and energy use, while warm water reduces it. The MET values come from typical pool temperatures, so an outdoor cold swim will cost more and a very warm pool slightly less.
Should rests at the wall count?
Use the time actually swimming. Long rests lower the average intensity, while short rests between sets are part of the session and can be included if you want the total for the pool visit.