Sports
Swim Performance Calculator
Calculate two-test critical speed, pace, target time, distance intercept, pool lengths, and a pace-linked SWOLF screen.
Two-test critical swim speed (m/s)-
Critical pace per 100 m (s)-
Projected target time at critical speed (s)-
Long-test pace per 100 m (s)-
Short-test pace per 100 m (s)-
Pool lengths in target swim-
Critical-speed time per pool length (s)-
Estimated SWOLF at critical pace-
Two-test distance intercept (m)-
Decision view
Two-test distance-time line, critical-speed slope, and target lane plan
Two-test distance-time line, critical-speed slope, and target lane planThe test points define a live slope while the target swim unfolds into pool lengths at the derived critical pace.
Exact scenario comparisonLong test time (s) changes while all other entered assumptions remain constant.
| Long test time (s) | Two-test critical swim speed (m/s) | Critical pace per 100 m (s) | Projected target time at critical speed (s) | Long-test pace per 100 m (s) | Short-test pace per 100 m (s) | Pool lengths in target swim | Critical-speed time per pool length (s) | Estimated SWOLF at critical pace | Two-test distance intercept (m) |
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How to use Swim Performance Calculator
- Perform a longer and shorter maximal test under similar conditions.
- Enter exact distances and seconds.
- Use the derived pace as a training reference, not a guaranteed race result.
Calculator guide
Understanding Swim Performance Calculator
Critical swim speed uses two maximal distance-time tests to estimate a sustainable speed boundary. The slope and intercept carry different performance information.
Detailed calculation process
Detailed two-test swim-performance calculation
The default uses 400 m in 420 s and 200 m in 200 s, then projects a 1,500 m swim in a 25 m pool.
General formula: CSS=(D_L-D_S)/(t_L-t_S)P_100=100/CSSt_target=D_target/CSSD'=D_S-CSS*t_SN_lengths=D_target/L_poolSWOLF=L_pool/CSS+S_L The line slope is distance gained per second. Its intercept represents modeled finite distance above the critical-speed component.
What each symbol means
Worked substitution with the default inputs
The default CSS is 0.9091 m/s, equivalent to 1:50 per 100 m, with a 27:30 modeled 1,500 m time.
Worked situations
Practical examples
- The default 400 m in 420 s and 200 m in 200 s give CSS=0.9091 m/s.
- That equals 110 s/100 m and projects 1,500 m in 1,650 s before fatigue or conditions.
Better inputs
Useful tips
- Separate tests with sufficient recovery.
- Use the same stroke and pool.
- Retest after a training block rather than adjusting one result.
Before relying on the result
Limitations and common mistakes
- Both tests must be maximal and the longer test slower per meter.
- Starts, turns, drafting, fatigue, technique, and open-water conditions are not modeled.
- SWOLF is pool-length and stroke-count specific.
Reference
Key terms
- Critical swim speed
- Slope of distance versus time between two tests.
- Distance intercept
- Finite modeled distance capacity above the critical-speed line.
- SWOLF
- Seconds per length plus strokes per length.
Important note
Use qualified coaching, safe testing conditions, appropriate medical clearance, and technique review for training decisions.
Frequently asked questions
Why can CSS be invalid?
Longer distance and time must both exceed the shorter test values.
Is CSS my exact 1,500 m pace?
No. It is a model-derived reference affected by fatigue and test quality.
Can SWOLF compare different pool lengths?
Not directly; turn frequency changes both time and strokes.