basic

Critical Swim Speed (CSS) from 200 m / 400 m Calculator

CSS = (D₂ − D₁) / (T₂ − T₁) = 200 / (T_400 − T_200).

Compute Critical Swim Speed — the swimmer's analogue of running's lactate threshold — from a 200 m and 400 m time-trial done back-to-back: CSS = (400 − 200) / (T_400 − T_200) m/s. Reports CSS in m/s, pace per 100 m, and the suggested CSS pace per 100 m for threshold sets.

Marcus Laurent By Marcus Laurent
Published Last reviewed 1 min read

Inputs

s
s

Results

Enter values and click Calculate to see results.
Was this helpful?

How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

CSS = 200 / (T_400 − T_200).

In depth

Compute Critical Swim Speed — the swimmer's analogue of running's lactate threshold — from a 200 m and 400 m time-trial done back-to-back: CSS = (400 − 200) / (T_400 − T_200) m/s. Reports CSS in m/s, pace per 100 m, and the suggested CSS pace per 100 m for threshold sets.