About

Swimming is one of the most energetically demanding activities due to the density of water, which is approximately 800 times denser than air. This tool allows swimmers to plan their sessions with precision. Unlike general trackers, this calculator differentiates between the specific biomechanics of four major strokes, recognizing that the Butterfly stroke burns nearly three times the energy of a leisurely backstroke.

A unique feature of this application is the "Laps to Goal" system. Instead of simply tracking time, you can input a caloric target (e.g., "I want to burn 400 kcal"), and the tool calculates exactly how many laps of a standard 25m, 50m, or 25-yard pool are required to meet that objective, based on your weight and stroke intensity.

Formulas

The core energy calculation uses the standard metabolic formula:

Kcal = MET × Weight_kg × Time_hr

To determine the "Laps to Goal," the equation is reversed. We solve for Time required to hit the Target Kcal, then estimate distance based on average swimming velocities (Approx. 2.5 km/h for moderate freestyle).

Time_req = TargetKcalMET × Weight

Laps = Time_req × VelocityPoolLength

Reference Data

Stroke	Intensity	METs	Burn/Hr (70kg)	Laps/Hr (Est)
Backstroke	Leisure/Moderate	4.8	336 kcal	40-50
Breaststroke	Moderate	5.3	371 kcal	40-50
Freestyle (Crawl)	Moderate	8.3	581 kcal	60-70
Freestyle (Crawl)	Vigorous/Fast	10.0	700 kcal	80+
Butterfly	General	13.8	966 kcal	50-60
Treading Water	Moderate	4.0	280 kcal	N/A
Sidestroke	General	7.0	490 kcal	50

Frequently Asked Questions

Yes. In water colder than body temperature (< 27°C / 80°F), your body expends additional energy on thermoregulation to maintain core heat. This calculator assumes a standard pool temperature; colder open-water swims may burn 5-10% more calories.

The Butterfly stroke is the most metabolically demanding (13.8 METs) due to the simultaneous engagement of the core, shoulders, and legs in a dolphin kick, requiring massive power to lift the body out of the water.

The lap count is an estimation derived from average swimmer speeds associated with specific MET intensities. An elite swimmer covers more distance per calorie than a beginner due to better hydrodynamic efficiency (less drag).