Critical Swim Speed (CSS)
​
CSS is your sustainable swim pace for long sets. Think of it as your “threshold pace” in the pool. This is approx your 1500m swim target time as well. We calculate it from two short time trials, a 200m and 400m. 

Enter your times below to get your CSS pace per 100m
Why it matters
  • Sets the right effort for aerobic development
  • Makes pacing simple and repeatable
  • Tracks progress across the season
​Step 1. Complete a solid warm up. Swim two time trials, 200m and 400m. Pro tip: Do the 200m first. And take at least 10, if not 30m active recovery between the two.
Step 2. Enter both distances and finish times.
Step 3. The tool gives you CSS pace per 100, plus per 50 and per 25, and a few target zones for training.
Coach tip: Re-test every 4 to 12 weeks and update your paces.

Critical Swim Speed (CSS) Calculator

Enter your 400 m and 200 m times (example: 6:15 or 2:55).