Estimate critical swim speed from matched 400 and 200 trials, or reverse-solve a trial time from a target pace per 100 meters or yards.
How the Critical Swim Speed Calculator Works
The two-point method treats the change in distance between a 400 and a 200 trial as 200 units, then divides that change by the difference between the two times. The equivalent pace per 100 is half the time difference.
| Output | Formula | Interpretation |
|---|---|---|
| Critical speed | 200 / (400 time − 200 time) | Distance units per second |
| CSS pace per 100 | (400 time − 200 time) / 2 | Practical training-pool display |
| Distance split | CSS pace × distance / 100 | Even-pace reference, not a race prediction |
Test setup
Use hard 400 and 200 efforts completed under comparable conditions, with enough recovery to preserve the protocol. Select meters when the trial distances are 400 m and 200 m, or yards when they are 400 yd and 200 yd.
Why the validation matters
The 400 time must exceed twice the 200 time. Otherwise the longer effort would have an equal or faster average pace, which makes the two-point CSS estimate unsuitable.
Sources
Source: Wakayoshi and colleagues, Does Critical Swimming Velocity Represent Exercise Intensity at Maximal Lactate Steady State?, European Journal of Applied Physiology, 1993.
