🏊Swim Pace Calculator

About this tool

Enter a distance in metres or yards and your time. The tool shows your pace per 100 (plus the other unit), your speed, and how long common distances take at that pace: 400 m, a mile, and sprint, Olympic, Ironman 70.3 and full Ironman swims. Add a 400 and a 200 time trial to get your Critical Swim Speed (CSS) and suggested training paces. Nothing is stored.

How swim pace and CSS work

Runners measure pace per kilometre or mile; swimmers measure it per 100 metres, or per 100 yards in many US pools. Pace per 100 = time ÷ distance × 100, so 1,500 m in 30:00 is 2:00 per 100 m. At that pace a sprint-triathlon 750 m takes 15 minutes and an Ironman 3.8 km about 1:16. Because 100 yd is only 91.44 m, yard paces look about 10% faster. Critical Swim Speed is a simple field test for your threshold, the fastest pace you can hold for roughly 30 minutes. Swim a hard 400 and, after recovering, a hard 200. Then CSS per 100 = (400 time − 200 time) ÷ 2. Times of 7:20 and 3:25 give 1:57.5 per 100 m. Coaches use CSS to set training paces: threshold sets such as 10 × 100 at CSS with short rest, and easy aerobic swimming 8–12 seconds per 100 slower. Retest every six to eight weeks. Honest limits: open-water pace is usually slower than in the pool (no push-offs, sighting, waves and currents), wetsuits usually make you faster, and tumble turns versus open turns change pool times. The pace calculator covers running and cycling, and the heart rate zone calculator and the calories burned calculator are related.

Frequently asked questions