Home / Swimming
Swimming Calculators
Swim pace and critical swim speed (CSS) calculators for pool and open-water training — find your threshold pace and per-100 splits in metres or yards, all in your browser.
Questions
What is critical swim speed (CSS)?
CSS is your sustainable threshold swim pace, estimated from a 400 m and a 200 m time trial. The CSS calculator returns your pace per 100 and the training paces to swim around it.
Can I use yards instead of metres?
Yes. Both swim tools switch between metres and yards, so they work for 25 m, 50 m, and 25-yard pools.
Are these swimming calculators free?
Yes — free, no sign-up, and run entirely in your browser.