How many calories does swimming, fast freestyle burn?

At 9.8 METs, a 70 kg person uses about 343 kcal in thirty minutes. Energy use scales with body weight, so a 90 kg person uses roughly a third more for the same session.

What is the MET value for swimming, fast freestyle?

9.8 METs, listed under Compendium code 18230. A MET is a multiple of resting metabolic rate.

Should I subtract my resting metabolism?

If you are adding this to a maintenance figure that already includes rest, yes. The net figure removes the roughly one MET-hour per hour your body would have spent anyway, which for swimming, fast freestyle leaves about 90 per cent of the gross total.

Why does body weight change the answer?

A MET value is energy per kilogram of body mass, so the same activity costs more for a heavier body. That is why weight is an input rather than an assumption, and why generic calories-burned figures without a weight are close to meaningless.

How accurate is this figure?

It is an estimate from a population average. Published comparisons against indirect calorimetry find individual discrepancies of twenty to thirty per cent, so use it to compare activities rather than as a ledger to eat back.

Calories burned swimming, fast freestyle

Swimming, fast freestyle is rated at 9.8 METs, meaning it costs about 9.8 times as much energy per minute as sitting still. Enter your weight and duration to turn that into kilocalories.

Result

These are estimates from population-level equations, not a measurement of you and not medical advice. Individual results vary widely. Talk to a doctor or a registered dietitian before making significant changes to how you eat or train.

The MET value and where it comes from

MET value: 9.8
Compendium code: 18230
Listed as: Swimming laps, freestyle, fast, vigorous effort
Category: Water

The Compendium assigns swimming, fast freestyle a value of 9.8 METs. One MET is what sitting quietly costs, so this activity is about 9.8 times that per minute of doing it.

kcal = MET × kg × h
     = 9.8 × weight × hours

net of resting:
kcal = (9.8 − 1) × weight × hours

Source: Herrmann SD, Willis EA, Ainsworth BE, et al. "2024 Adult Compendium of Physical Activities." Journal of Sport and Health Science 13(1), 2024, pp. 6–12. MET values are population averages; roughly 18% of Compendium entries are estimated rather than measured.

The figure above is gross energy — everything spent during the session, including the resting metabolism you would have used anyway. Subtracting one MET-hour per hour gives what swimming, fast freestyle actually added.

The 9.8 MET figure for swimming, fast freestyle is a population average. The Compendium itself notes that individual energy cost varies with fitness, technique, terrain and body composition, so treat it as an order of magnitude rather than a measurement.

Calories burned by body weight and duration

Gross energy in kilocalories. Read across from your weight and down from your duration. A 70 kg person uses about 686 kcal an hour, of which roughly 616 is above what resting would have cost.

Calories burned by body weight and duration
Body weight	15 min	20 min	30 min	45 min	60 min	90 min
55 kg	135	180	270	404	539	809
65 kg	159	212	319	478	637	956
75 kg	184	245	368	551	735	1,103
85 kg	208	278	417	625	833	1,250
95 kg	233	310	466	698	931	1,397
110 kg	270	359	539	809	1,078	1,617

Compared with related activities

Energy used per thirty minutes at 70 kg, so the activities are directly comparable.

Comparison with related activities
Activity	METs	kcal / 30 min
Swimming, fast freestyle	9.8	343
Swimming, slow freestyle	5.8	203
Rowing machine	7.3	256
Running at 11 km/h	11	385
Cycling, vigorous effort	10	350
Water aerobics	5.3	186

Questions

How many calories does swimming, fast freestyle burn?: At 9.8 METs, a 70 kg person uses about 343 kcal in thirty minutes. Energy use scales with body weight, so a 90 kg person uses roughly a third more for the same session.
What is the MET value for swimming, fast freestyle?: 9.8 METs, listed under Compendium code 18230. A MET is a multiple of resting metabolic rate.
Should I subtract my resting metabolism?: If you are adding this to a maintenance figure that already includes rest, yes. The net figure removes the roughly one MET-hour per hour your body would have spent anyway, which for swimming, fast freestyle leaves about 90 per cent of the gross total.
Why does body weight change the answer?: A MET value is energy per kilogram of body mass, so the same activity costs more for a heavier body. That is why weight is an input rather than an assumption, and why generic calories-burned figures without a weight are close to meaningless.
How accurate is this figure?: It is an estimate from a population average. Published comparisons against indirect calorimetry find individual discrepancies of twenty to thirty per cent, so use it to compare activities rather than as a ledger to eat back.