CRITICAL SWIM SPEED CALCULATOR

Critical Swim Speed (CSS) is an estimate of the fastest pace a swimmer can sustain for an extended period without exhaustion. It is often used in training to set pacing targets for endurance swimming. CSS is calculated based on two time trials—typically 400m and 200m swims—to determine a swimmer’s threshold speed. By training at or near CSS, swimmers can improve their aerobic capacity and overall endurance.

To use the calculator below, you will need to perform a 400m and 200m time trial with plenty of rest between them. The result will be given in m/s and min/100m and will reflect the rough pace you should be able to sustain in the swim leg of an standard distance triathlon.

If you have a tempo trainer (a mentronome that sits under your swim cap) or smart goggles, CSS can be used to set your swim pacings for structured workouts.