Can I calculate my swim time or distance, not just pace?

Yes. The calculator has three modes: enter pace plus distance to get total time, enter pace plus time to get distance, or enter distance plus time to get your pace per 100m. Pick the mode for whichever value you already know and it solves for the other.

How do I read my swim pace per 100m?

Pace per 100m is your time to cover 100 metres at the set's average speed — the standard pacing unit swimmers use to compare sets across distances. The calculator also returns pace per 100yd so you can compare metric and yard-pool workouts side by side.

Can I use yards instead of meters?

Yes. The calculator supports both meters and yards, and always returns pace for both 100m and 100yd so you can compare workouts.

What if I only know laps and pool length?

Switch to laps mode and enter lap count plus pool length. The calculator converts that into total distance automatically.

How is SWOLF estimated?

SWOLF is estimated from your pace, distance, stroke type, and pool length assumptions. It is a planning estimate, not a replacement for watch-based stroke counts.

What does the effort zone mean?

Effort zone classifies pace intensity from Recovery to Sprint using your pace per 100m. It helps you align sets with easy, tempo, threshold, or sprint work.

Methodology: Swim Pace Calculator

Scope

Calculates swim pace, total time, or distance for any two of the three, with SWOLF and effort context.

Formula

pace_per_100 = total_time / distance * 100. SWOLF = stroke_count + seconds per length.

Coefficients

Parameter	Value	Note
Pool length options	`25 m, 50 m, 25 yd`

Data sources

World Aquatics (formerly FINA) — Facilities Rules: pool dimensions and timing standards. — Federation specification for 25 m, 50 m, and short-course pool lengths and competition timing.
USA Swimming — Rules and Regulations: course-length and timing standards. — U.S. governing body for swimming course measurement and meet-time standards.

Assumptions

Pool length is accurate; open-water GPS adds substantial noise.

Approximation range

Arithmetic is exact; SWOLF trends reflect stroke efficiency over sessions.

Limitations

Pace does not capture stroke type, open-water conditions, or currents.

Reproducibility

1000 m in 18:00. Pace = 18*60/10 = 108 s/100 m = 1:48/100 m.

Change log

2026-04-24: methodology page first published.

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Worked example

Computed by the same engine bundle served at /engines/swim-pace-calculator.js. Re-runnable: the values below are the literal output of compute(engineInput).

Input

tool: swim_pace_calculator
mode: pace
stroke_type: freestyle
distance_value: 1500
distance_unit: m
laps: 0
pool_length: 25
pool_length_unit: m
time_seconds: 1800
target_pace_seconds: 120
target_pace_unit: 100m

Output

distanceMeters: 1500
distanceYards: 1640.42
totalTimeSeconds: 1800
pacePer100mSeconds: 120
pacePer100ydSeconds: 109.73
swolfEstimate: 50
effortZone: Tempo
strokeType: freestyle

FAQ

Can I calculate my swim time or distance, not just pace?: Yes. The calculator has three modes: enter pace plus distance to get total time, enter pace plus time to get distance, or enter distance plus time to get your pace per 100m. Pick the mode for whichever value you already know and it solves for the other.
How do I read my swim pace per 100m?: Pace per 100m is your time to cover 100 metres at the set's average speed — the standard pacing unit swimmers use to compare sets across distances. The calculator also returns pace per 100yd so you can compare metric and yard-pool workouts side by side.
Can I use yards instead of meters?: Yes. The calculator supports both meters and yards, and always returns pace for both 100m and 100yd so you can compare workouts.
What if I only know laps and pool length?: Switch to laps mode and enter lap count plus pool length. The calculator converts that into total distance automatically.
How is SWOLF estimated?: SWOLF is estimated from your pace, distance, stroke type, and pool length assumptions. It is a planning estimate, not a replacement for watch-based stroke counts.
What does the effort zone mean?: Effort zone classifies pace intensity from Recovery to Sprint using your pace per 100m. It helps you align sets with easy, tempo, threshold, or sprint work.