Swim Pace Calculator
Pace per 100m and per km plus speed from swim distance and time.
What it does
Swim training speaks per hundred meters because pools measure in 25s and 50s. Total seconds divided by hundreds swum gives the pace that intervals, test sets, and race plans all quote.
The tool above takes distance with minutes and seconds. It returns pace per 100m, per km, and speed in meters per second.
Critical swim speed approximates threshold from a 200 plus 400 time trial pair. It sets sustainable interval paces the way FTP sets cycling zones.
Open water adds sighting, chop, and wetsuit buoyancy over pool numbers. Rough days cost seconds per hundred that no pool math predicts.
How to use
- Enter the swim distance in meters.
- Enter minutes with leftover seconds.
- Read per 100m for intervals and per km for races.
- Add open water margin on race day.
Formula
- meters / 100
- Hundreds swum dividing the clock.
- speed
- Meters per second for direct comparison.
Touch turns versus open turns shift pool times by seconds per hundred. Race open water removes walls entirely.
Worked example
Example: 400 m in 8:00
Four hundred meters in eight minutes flat.
- Seconds: 8 x 60 = 480.
- Hundreds: 400 / 100 = 4.
- Pace: 480 / 4 = 120 s, shown as 2:00 per 100m.
- Per km: 480 / 0.4 = 1200 s, shown as 20:00. Speed 400/480 = 0.83 m/s.
Reference table
| 400 m | Per 100m | Level |
|---|---|---|
| 5:20 | 1:20 | Fast club |
| 6:40 | 1:40 | Strong amateur |
| 8:00 | 2:00 | Regular swimmer |
| 10:00 | 2:30 | Steady beginner |
| 12:00 | 3:00 | Learning ropes |
Limits
- Pool assumptions. Open water varies widely.
- Turn technique moves times seconds per hundred.
- Wetsuits add buoyancy and speed.
- Drafting legal races run faster.
Common mistakes
- Sprinting test sets without warmup.
- Comparing pool and open water directly.
- Ignoring rest intervals in set averages.
- Chasing pace with sinking legs.
- Skipping technique for yardage.
Try it yourself
Quick checks. Answers sit tucked under each question.
200 m in 3:30?
210 s / 2 = 105 s, so 1:45 per 100m.
Speed there?
200 / 210 = 0.95 m/s.
Questions
What is a good 100m pace?
Near 1:30 for fit amateurs, 2:00 regular, under 1:10 fast.
How do I pace a triathlon swim?
Slightly easier than pool threshold. Sighting costs energy.
What is CSS?
Critical swim speed: threshold pace from 200 plus 400 trials.
Does wetsuit help pace?
Yes seconds per hundred from buoyancy, mainly for weaker kickers.
How do turns affect time?
Good turns save seconds per hundred over open turns.
How often should I test?
Monthly 400 time trials track training blocks.