Calculate swim pace per 100m/yd, total time, and split targets for pool and open water.
Swim pace is the time it takes to cover one 100 m or 100 yd, and nearly everything else in a swimmer's plan follows from that single ratio. This tool takes the two numbers you know, usually a distance and an elapsed time, and returns the per-100 pace, the total time for any other distance, and split targets you can check against the clock at each wall. The one thing that trips people up first is the unit: a 2:00 pace in a yards pool is not the same effort as 2:00 in meters, since a yard is only 0.9144 m.
A concrete input and expected output from the current implementation.
Input
1500 m swum in 31:30
Expected output
Pace: 2:06 per 100 m. 400 m race: 8:24. 5 x 100 m set: 2:06 per repeat, 10:30 total. 2.4 km open-water leg: 50:24.
31:30 is 1890 seconds and 1500 m is 15 blocks of 100 m, so 1890 / 15 = 126 seconds, or 2:06, per 100 m. Every other figure is 126 seconds times the number of 100 m blocks in that distance: 4 blocks gives 504 seconds (8:24), 5 gives 630 (10:30), and 24 gives 3024 (50:24).
Pace is elapsed time divided by distance in 100-unit blocks: 1500 m swum in 31:30 is 1890 seconds over 15 blocks, or 126 seconds (2:06) per 100 m. Total time multiplies the same ratio back out, so a 400 m swim is 4 x 126 = 504 seconds. Splits, race totals, and open-water leg estimates are all that one number reused.
The meters-versus-yards choice is a real conversion, not a label change. The international yard is exactly 0.9144 m, so the same effort reads about 9 percent faster per 100 yd: 1:50 per 100 yd equals roughly 2:00 per 100 m. Split targets scale by repeat count: a 2:06 per-100 target becomes 1:03 per length in a 50 m pool and 31.5 seconds per length in a 25 m pool.
Use meters for anything race-related. A pace that feels like 1:50 per 100 yd is about 2:00 per 100 m, and planning a meters race with yards numbers gives splits roughly 9 percent too fast to hold. Your effort does not change; only the number on the clock does.
As targets, yes; as guarantees, no. The tool assumes you can hold the same per-100 time on every repeat, and fatigue erodes that in any set past a few hundred meters. Leave a couple of seconds of cushion per 100 early on, or treat the total time as the goal and let individual splits drift.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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