You enter your body weight in pounds, choose a stroke and intensity, and set a duration. The tool converts weight to kilograms, looks up the MET value for your stroke and intensity from the Compendium of Physical Activities, and computes calories as (MET × weight in kg × minutes) ÷ 60. A walking comparison at MET 4.0 is subtracted to show the extra burn from swimming.
Butterfly engages the entire body in a powerful undulating motion with simultaneous arm recovery above water. It demands more muscular effort per stroke than any other style, which is why its MET values are the highest of the four competitive strokes.
Yes. Cold water forces your body to generate extra heat, slightly increasing calorie expenditure. Very warm water (above 84°F / 29°C) can reduce efficiency by raising core temperature too quickly. Most pools are kept between 78–82°F for lap swimming.
For the most accurate result, count only the time you are actively swimming. If your workout includes substantial rest between sets, the total burn will be lower than a continuous-swim estimate.
Moderate-pace freestyle (MET 8.3) burns roughly the same as running at 5.5 mph (MET 8.3). Vigorous butterfly (MET 13.8) approaches the burn rate of running at 8+ mph. Swimming has the added benefit of being low-impact on joints.
Estimate only. Results reflect your inputs and standard formulas — they are not financial, tax, legal, health, or investment advice. Verify important decisions with a qualified professional.