Enter a swim distance and your total time to calculate pace per 100m.
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CSS is your lactate threshold in the water — estimated from two max-effort time trials (400m and 200m).
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How to use the Swimming Pace Calculator
- Time → Pace: Enter total swim time and distance to get pace per 100m and 100yd.
- Pace → Time: Enter pace per 100m and distance to predict total time.
- CSS: Calculate Critical Swim Speed from two time trials for threshold-based training.
What is CSS?
Critical Swim Speed is the fastest pace you can theoretically sustain indefinitely — your aerobic threshold in swimming. It's calculated as: CSS = (400m − 200m) ÷ (T400 − T200) where T is time in seconds. You should do most endurance swim training at or just below your CSS pace.