Swim Pace Calculator
Enter a swim distance and time to get your pace per 100 m and per 100 yards and your speed, or enter a pace to get your finish time.
Type h:mm:ss or mm:ss, like 1:05:00 or 28:30. Tenths are fine (3:10.5). A plain number means minutes.
Pace as m:ss, like 1:45 or 1:45.5.
Critical Swim Speed (CSS) and training paces
Warm up well, swim a 400 flat out, rest 5–10 minutes, then swim a 200 flat out. Enter both times.
| Set type | Per 100 m | Per 100 yd |
|---|
CSS = (400 − 200) ÷ (400 time − 200 time). The training bands (CSS plus or minus a few seconds per 100) follow common coaching practice, not a fixed rule. Retest every 6–8 weeks.
Pool lengths and laps
A length is one end to the other. In the US a “lap” often means one length; in many other places a lap is there and back (two lengths). Both are shown.
Split times
0 = even pace. A minus number means a slower second half.
| Split | At | Split time | Total time | Pace |
|---|
Stroke rate and distance per stroke (optional)
Count every arm entry (left and right) for a minute, or read it from your watch. Many adult freestyle swimmers sit around 50–70.
Real stroke counts per length are lower, because the push-off and glide from the wall carry you the first few metres for free. SWOLF = strokes per length + seconds per length; lower is better.
How your swim pace is worked out
Pace per 100 = time ÷ (distance ÷ 100).
- 1
Time in seconds
30:00= 1,800 s
- 2
Distance in 100s
1,500 m= 15 × 100 m
- 3
Pace per 100 m
1,800 s ÷ 15= 120 s= 2:00 /100 m
- 4
Per 100 yd and speed
120 s × 0.9144= 1:49.7 /100 yd= 3.00 km/h
Read more: the formula, a worked example, CSS, pool laps and stroke rate
Swimmers measure pace as the time for each 100 metres (or 100 yards in many US pools). It is the swimming version of running pace per km. Speed is the same thing flipped over: how far you go in an hour. For running pace, use the running pace calculator.
The formula
pace per 100 m = time in seconds ÷ (distance in metres ÷ 100)
pace per 100 yd = pace per 100 m × 0.9144
finish time = pace per 100 × (distance ÷ 100)
speed in km/h = distance in km ÷ time in hours
CSS (m/s) = (400 − 200) ÷ (400 time − 200 time)
lengths = distance ÷ pool length
Worked example
You swim 1500 m in 30:00. That is 30 × 60 = 1,800 seconds over 1,500 ÷ 100 = 15 hundreds, so your pace is 1,800 ÷ 15 = 120 seconds, or 2:00 per 100 m. Per 100 yards it is 120 × 0.9144 = 109.728 seconds, or 1:49.7 per 100 yd. Your speed is 1.5 km ÷ 0.5 hours = 3.00 km/h, which is 3 ÷ 1.609344 = 1.86 mph (0.83 m/s). In a 25 m pool that is 1,500 ÷ 25 = 60 lengths, each taking 30 seconds.
Finish time from a pace
- Ironman (3.8 km) at 1:45 per 100 m: 105 × 38 = 3,990 seconds, which is 1:06:30.
- Olympic triathlon (1500 m) at 1:45: 105 × 15 = 1,575 seconds, which is 26:15.
Critical Swim Speed (CSS)
Swim a 400 in 6:40 (400 s) and a 200 in 3:10 (190 s). CSS = 200 ÷ (400 − 190) = 200 ÷ 210 = 0.952 m/s. Pace per 100 m is 100 ÷ (200 ÷ 210) = 210 ÷ 2 = 105 seconds, or 1:45.0 per 100 m. Common coaching bands around that CSS:
| Set type | CSS offset | Per 100 m (CSS 1:45) |
|---|---|---|
| Easy / recovery | +10 to +15 s | 1:55–2:00 |
| Endurance | +5 to +8 s | 1:50–1:53 |
| Threshold (CSS) | 0 to +2 s | 1:45–1:47 |
| Fast (above CSS) | −5 to −2 s | 1:40–1:43 |
| Sprint | −12 to −8 s | 1:33–1:37 |
Stroke rate
Distance per stroke = speed × 60 ÷ stroke rate. At 0.833 m/s and 60 strokes a minute, each stroke moves you 0.833 × 60 ÷ 60 = 0.83 m, so a 25 m length is 25 ÷ 0.83 = 30 strokes in 30 seconds (SWOLF 60) if you had no push-off.
Common paces
| Per 100 m | Per 100 yd | km/h | 750 m | 1500 m | 1.9 km | 3.8 km |
|---|---|---|---|---|---|---|
| 1:30 | 1:22.3 | 4.00 | 11:15 | 22:30 | 28:30 | 57:00 |
| 1:45 | 1:36.0 | 3.43 | 13:08 | 26:15 | 33:15 | 1:06:30 |
| 2:00 | 1:49.7 | 3.00 | 15:00 | 30:00 | 38:00 | 1:16:00 |
| 2:30 | 2:17.2 | 2.40 | 18:45 | 37:30 | 47:30 | 1:35:00 |
| 3:00 | 2:44.6 | 2.00 | 22:30 | 45:00 | 57:00 | 1:54:00 |
Pool or open water
Pool times include a push-off from the wall every length, which is free speed. In open water there are no walls, you lift your head to sight, and waves, currents and other swimmers slow you down, so most people swim a little slower there without a wetsuit. A wetsuit adds buoyancy and often makes you faster. Race courses are also not always measured exactly.
Results assume a steady pace. CSS training bands are a common rule of thumb from coaching practice, not a medical or personal training plan.
Common questions
How do I work out my swim pace per 100 m?
Divide your time in seconds by the number of hundreds you swam. 1500 m in 30:00 is 1,800 seconds ÷ 15 = 120 seconds, or 2:00 per 100 m. Multiply by 0.9144 for pace per 100 yards: 1:49.7 per 100 yd. Your speed is 1,500 m ÷ 1,800 s = 0.83 m/s, or 3.00 km/h.
How long will an Ironman swim take me?
Multiply your pace per 100 m by 38, because the Ironman swim is 3.8 km. At 1:45 per 100 m that is 105 × 38 = 3,990 seconds, or 1:06:30. A 70.3 swim (1.9 km) at the same pace takes 105 × 19 = 1,995 seconds, or 33:15. Open water with a wetsuit can be a little faster or slower than the pool.
What is Critical Swim Speed (CSS)?
CSS is roughly the fastest pace you can hold for a long time without tiring fast, a bit like a threshold pace. Swim a 400 and a 200 flat out with a rest between. CSS = 200 ÷ (400 time − 200 time) in metres per second. With 6:40 and 3:10: 200 ÷ (400 − 190) = 0.952 m/s, which is 1:45.0 per 100 m.
What training paces should I use from my CSS?
A common coaching approach sets paces as CSS plus or minus a few seconds per 100 m: easy around CSS +10 to +15 s, endurance +5 to +8 s, threshold sets at CSS to +2 s, faster repeats 2 to 5 s quicker than CSS and sprints 8 to 12 s quicker. Treat these as a guide and retest every 6 to 8 weeks.
How many lengths is 1500 m in a 25 m pool?
1,500 ÷ 25 = 60 lengths. If a lap means there and back, that is 30 laps. In a 50 m pool it is 30 lengths. In a 25 yard pool (22.86 m) it is 65.6 lengths, so you would swim 66 lengths to cover at least 1500 m.
Is open-water swimming slower than the pool?
Usually, yes, without a wetsuit. In open water there are no walls to push off, you need to look up to sight, and waves, currents and other swimmers slow you down. A wetsuit adds buoyancy and often makes you faster. Use your pool pace as a starting point, then check it with an open-water swim.
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