Swimming Pace Zone Calculator

Discover your Critical Swim Speed (CSS) and determine your optimal swim training zones in meters or yards with this easy-to-use calculator.

A CSS test is a straightforward method to assess your swimming fitness level. It predicts the pace per 100 you could sustain during an all-out 1500-meter or yard time trial.

To measure your CSS pace, perform a maximum effort 400 and 200 swim time trial in the same session, with a five-minute active recovery between each. Record your times for both distances, then input them into the calculator below to reveal your results!