The estimates don't stop at freestyle. Generally, swimmers will burn the same amount of calories doing backstroke than they will doing a slower freestyle, according to Nutristrategy.
Swimming breaststroke for an hour will burn a similar amount of calories to doing a fast freestyle workout.
For the king of calorie-burning swimming workouts, though, swim an hour doing butterfly (if you dare). The calorie torching ranges from 649 calories for a 130-pounder to 1,024 calories for a 205-pounder.
How Does it Compare to Other Sports?
With those numbers in mind, is swimming the best option for someone looking to burn calories?
Well, no—of all the activities Nutristrategy documents, cross-country skiing uphill burns the most (have fun doing that!). But among the most common endurance sports disciplines, swimming holds its own.
Running for an hour at a 9:00/mile pace burns anywhere from 649 to 1,024 calories depending on your weight, and the amount of calories burned naturally goes up the faster you go. This is in line with the widely held belief that running is the best endurance sport for weight loss.
Cycling for an hour at 15 miles per hour will burn anywhere from 590 to 931 calories depending on weight.
Swimming is right in the discussion, and considering how easy the sport is on your joints, it's a workout you can enjoy doing—while knowing that you're getting results.