Formula, in endurance

Swim Pace Formula

Swim pace is time per 100 m. Open-water and pool times don't translate directly — open water adds 5–15 sec per 100 m depending on conditions, sighting, and chop.

3 variables. Published Mar 12, 2026. Updated May 10, 2026. By AI Fit Hub.

Education, not medical advice. The result comes only from the published formula and your inputs. How we check our formulas.

Formula

pace_per_100m = total_time_seconds × 100 / total_distance_m

Variables

pace_per_100m

Pace per 100 m

Seconds (or min:sec) per 100 meters. Standard swim pace unit. Pool swim 1:30/100m is moderate, 1:15/100m advanced, sub-1:00 elite.

total_time

Elapsed time

Seconds for the swim set. Convert minutes by × 60.

total_distance

Distance covered

Meters (or yards). 1 yard = 0.9144 m. Pool pace in a 25-yard pool is ~9% faster than in a 25-meter pool.

Step by step

1

Time the full swim set in seconds.

1,500 m in 27:30 = 1,650 seconds.
2

Divide by total distance, multiply by 100.

1,650 × 100 / 1,500 = 110 sec per 100 m.
3

Convert seconds to minutes:seconds for readability.

110 sec = 1:50 per 100 m.
4

For open-water predictions, add a conditions surcharge: +5 sec calm flatwater, +10 sec moderate chop, +15+ sec ocean conditions or strong current.

Calm open-water predicted pace: 1:55 per 100 m.

Worked example

1,500 m pool swim in 27:30

Distance (m)

1,500

Total time

27:30

pace = 1,650 × 100 / 1,500 = 110 sec/100m = 1:50/100m

Pool pace 1:50 per 100 m. Open-water equivalent in calm conditions: roughly 1:55 per 100 m.

Common variations

Critical Swim Speed (CSS): from 400 m and 200 m time-trial times, estimate threshold pace. CSS = (D400 − D200) / (T400 − T200).

Swolf score: stroke count + seconds per length. Efficiency metric — lower is better, but stroke length and rate trade off.

Open-water sighting cost: every sighting stroke costs 0.5–1 sec. Plan to sight every 6–8 strokes in straight courses, every 3–4 in winding ones.

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Sources

Wakayoshi K et al. A simple method for determining critical speed as swimming fatigue threshold in competitive swimming , International Journal of Sports Medicine (1992)
Maglischo EW. Swimming Fastest , Human Kinetics