How swim pace is calculated
Swimmers measure pace as the time it takes to swim 100 metres or 100 yards. Divide your time by the distance and multiply by 100:
Pace per 100 = time ÷ distance × 100
A 1500 m swim in 25:00 is 1500 seconds ÷ 1500 × 100 = 100 seconds, or 1:40 per 100 m. The same pace predicts your time for any other distance, although real race times slow down as distances get longer.
Swim times by pace and distance
What a given pace per 100 m comes to over the race distances, from a sprint triathlon to an Ironman. The triathlon swims are set in miles — 1.2 for a 70.3 and 2.4 for a full — so they work out at 1,931 m and 3,862 m rather than the round 1,900 and 3,800 often quoted.
| Per 100 m | 750 m sprint | 1500 m Olympic | 1.2 mi (70.3) | 2.4 mi (Ironman) |
|---|---|---|---|---|
| 1:10 | 8:45 | 17:30 | 22:32 | 45:04 |
| 1:15 | 9:23 | 18:45 | 24:08 | 48:17 |
| 1:20 | 10:00 | 20:00 | 25:45 | 51:30 |
| 1:25 | 10:38 | 21:15 | 27:22 | 54:43 |
| 1:30 | 11:15 | 22:30 | 28:58 | 57:56 |
| 1:35 | 11:53 | 23:45 | 30:35 | 1:01:09 |
| 1:40 | 12:30 | 25:00 | 32:11 | 1:04:22 |
| 1:45 | 13:08 | 26:15 | 33:48 | 1:07:36 |
| 1:50 | 13:45 | 27:30 | 35:24 | 1:10:49 |
| 1:55 | 14:23 | 28:45 | 37:01 | 1:14:02 |
| 2:00 | 15:00 | 30:00 | 38:37 | 1:17:15 |
| 2:05 | 15:38 | 31:15 | 40:14 | 1:20:28 |
| 2:10 | 16:15 | 32:30 | 41:51 | 1:23:41 |
| 2:15 | 16:53 | 33:45 | 43:27 | 1:26:54 |
| 2:20 | 17:30 | 35:00 | 45:04 | 1:30:07 |
| 2:25 | 18:08 | 36:15 | 46:40 | 1:33:21 |
| 2:30 | 18:45 | 37:30 | 48:17 | 1:36:34 |
| 2:35 | 19:23 | 38:45 | 49:53 | 1:39:47 |
| 2:40 | 20:00 | 40:00 | 51:30 | 1:43:00 |
| 2:45 | 20:38 | 41:15 | 53:07 | 1:46:13 |
| 2:50 | 21:15 | 42:30 | 54:43 | 1:49:26 |
| 2:55 | 21:53 | 43:45 | 56:20 | 1:52:39 |
| 3:00 | 22:30 | 45:00 | 57:56 | 1:55:52 |
Read it as a flat-pace projection, not a prediction. Pace drifts over a long swim, and an open-water swim adds sighting, chop and a line that is never quite straight — most swimmers are a little slower over 2.4 miles than this chart suggests from a pool 100.
Metres or yards?
Most pools outside the US are 25 m or 50 m; many US pools are 25 yards. One yard is 0.9144 m, so 100 yd is 91.44 m and a pace per 100 yd looks about 9% faster than the same effort per 100 m. The calculator shows both.
Finding your CSS (critical swim speed)
Critical swim speed is an estimate of your threshold pace — roughly the fastest pace you can keep up for a long continuous swim. It comes from the idea of critical velocity (Wakayoshi et al., 1992): distance and time rise in a nearly straight line, and the slope of that line is your sustainable speed. The simple field version uses two time trials:
- Warm up well, then swim 400 all-out from a push start and note the time.
- Recover fully with easy swimming.
- Swim 200 all-out and note the time.
CSS speed = (400 − 200) ÷ (T400 − T200)
CSS pace per 100 = (T400 − T200) ÷ 2
For example, 6:00 for 400 and 2:50 for 200 gives (360 − 170) ÷ 2 = 95 seconds, or 1:35 per 100. Coaches set interval paces a few seconds either side of CSS, and repeat the test every 6–8 weeks as you get fitter.
CSS from a 400/200 test tends to come out slightly faster than a true long-distance threshold, so treat it as an upper limit for steady swims.
Frequently asked questions
How do I calculate my swim pace?
Divide your time by the distance and multiply by 100. For example, 1500 m in 25:00 is 1500 seconds ÷ 1500 m × 100 = 100 seconds, or 1:40 per 100 m.
What is critical swim speed (CSS)?
CSS is an estimate of your threshold pace: roughly the fastest pace you can hold for a long continuous swim without fading. It comes from the slope of your 400 and 200 time trials, and coaches use it to set interval paces.
How do I convert pace per 100 yards to per 100 metres?
100 yards is 91.44 metres, so a pace per 100 yd is about 9% faster on paper than the same effort per 100 m. Divide a yard pace by 0.9144 to get the metre pace.
Sources
The formula on this page comes from the published work below. We check the numbers against the worked examples in these sources with automated tests, and re-read the page against them when we review it.
- Wakayoshi K, Ikuta K, Yoshida T, et al. Determination and validity of critical velocity as an index of swimming performance in the competitive swimmer. Eur J Appl Physiol Occup Physiol. 1992;64(2):153–157. pubmed.ncbi.nlm.nih.gov/1555562/
- Wakayoshi K, Yoshida T, Udo M, et al. A simple method for determining critical speed as swimming fatigue threshold in competitive swimming. Int J Sports Med. 1992;13(5):367–371. pubmed.ncbi.nlm.nih.gov/1521952/
General fitness information, not medical advice. Results are estimates; check with a doctor or qualified coach before major changes to diet or training. Formula and copy last reviewed 31 October 2026.