OmniathlonOWS

Swim Pace Calculator

Three numbers that always fit together: pace, time and distance. Enter two of them and the third comes out on its own: you swam a distance in a given time and want your pace, you're planning a race and want to know how long it'll take, or you have a fixed window — a tide, a sunset — and want to know how far it gets you.

Distance
Time
h
m
s
min/100 m
2:00
min/km
20:00
m/s
0.83
min/100 yd
1:50
km/h
3
mph
1.86

What pace is, and why it matters

Pace is your speed told backwards: not how far you go in an hour, but how long a fixed stretch — a hundred metres, usually, because that's the unit coaches and swimmers actually think in — costs you. Two swimmers who finish a 5 km race at different times held different paces for the whole course: pace is that number, not the final placing. Knowing it is useful for two very practical things: comparing two sessions swum at different distances (a 400 repeat and a 1500 repeat compare on pace, not on raw time), and estimating ahead of time a race you haven't swum yet.

Before you enter: the sum worth doing first

Many open water races have a cutoff time to complete the course. Take your most realistic pace — not your personal best, the one you hold when you're tired halfway through — and multiply it by the distance: that's the check to make before you pay the entry fee, not halfway through the race when it's too late to change plan.

Pool pace isn't open water pace

If your only reference is the pool, expect a different number in the sea or a lake: you lose the push-off from the wall every length, you swim with your head up more often to sight, and conditions such as current, wetsuit and temperature all change what every stroke costs you. That's not a limit of this calculator — it's the physics of a different environment. For an estimate that accounts for current, wetsuit and water type, the next step is the Crossing Time Predictor.

Frequently asked questions

›Does pace change between the pool and open water?

Yes, almost always — see the section above: you lose the wall push-off, your body position changes to breathe and sight, and there are variables like current and temperature that don't exist in a pool. The Crossing Time Predictor folds these into the estimate.

›Should I use min/100 m or km/h?

They're the same information written two ways. Pool swimmers usually think in min/100 m or min/100 yd (the American unit); people planning a long crossing often prefer km/h, since it's closer to how a nautical chart reads. The calculator shows you all of them together on purpose.

›Why isn't there a comparison with elite swimmers' times?

Because a meaningful comparison needs a verified, comparable figure, and the fastest open water swimmers' times shift with the course, the day's conditions and the exact distance. An average would be invented, not measured — so we leave it out.

›Does the calculator account for current or a wetsuit?

No, on purpose: this one is deterministic, the same arithmetic you'd do by hand, meant for reading what you already swam or planning without extra variables. To fold in current, wetsuit and water type as a forecast, use the Crossing Time Predictor.

›Can I use miles and yards?

Yes: the unit selector covers both metric and imperial, including pace per 100 yards, the standard in American pools.

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