SWOLF & Stroke Efficiency Calculator
SWOLF alongside the two honest numbers underneath it — because one score covers swims twice as fast as each other.
Count strokes the way you always count them and stay consistent — some swimmers count one arm, some count both, and the score only means anything against your own previous scores anyway. Nothing is uploaded.
The same score describes opposite swims
SWOLF is seconds plus strokes — a duration added to a tally, which is why the result has no units and cannot be converted into anything. It also means one score covers a great many different swims. Every row below scores exactly 40 over a 25 m length, and they range from 0.78 m/s to 1.79 m/s.
| Seconds | Strokes | SWOLF | Speed | Per stroke | Rate |
|---|---|---|---|---|---|
| 14 | 26 | 40 | 1.79 m/s | 0.96 m | 111 spm |
| 16 | 24 | 40 | 1.56 m/s | 1.04 m | 90 spm |
| 18 | 22 | 40 | 1.39 m/s | 1.14 m | 73 spm |
| 20 | 20 | 40 | 1.25 m/s | 1.25 m | 60 spm |
| 22 | 18 | 40 | 1.14 m/s | 1.39 m | 49 spm |
| 24 | 16 | 40 | 1.04 m/s | 1.56 m | 40 spm |
| 26 | 14 | 40 | 0.96 m/s | 1.79 m | 32 spm |
| 28 | 12 | 40 | 0.89 m/s | 2.08 m | 26 spm |
| 30 | 10 | 40 | 0.83 m/s | 2.50 m | 20 spm |
| 32 | 8 | 40 | 0.78 m/s | 3.13 m | 15 spm |
The fastest of those takes the most strokes and the slowest glides furthest per stroke — a sprinter and a cruiser, indistinguishable to the score. The trade is exactly one stroke per second, which is not a fair exchange in any pool: a second is worth far more to a race than a stroke is.
Which is not to say it is useless — only that it is yours alone
Hold the time and it tracks the stroke; hold the stroke and it tracks the speed. Against your own previous scores, at the same pool and the same stroke, a falling SWOLF is real progress. Across pools it is nothing: the identical swim — same speed, same distance per stroke — scores differently in a 50 m pool than a 25 m one, because both halves of the sum double.
| Swim | SWOLF | Speed | Per stroke |
|---|---|---|---|
| 18s, 18 strokes | 36 | 1.39 m/s | 1.39 m |
| 20s, 16 strokes | 36 | 1.25 m/s | 1.56 m |
| 22s, 14 strokes | 36 | 1.14 m/s | 1.79 m |
| 24s, 12 strokes | 36 | 1.04 m/s | 2.08 m |
| 20s, 20 strokes | 40 | 1.25 m/s | 1.25 m |
| 24s, 18 strokes | 42 | 1.04 m/s | 1.39 m |
If you want a number that survives being compared, use the two underneath it instead. Distance per stroke is metres and stroke rate is per minute — both are honest units, both convert, and between them they say everything SWOLF says without the ambiguity of adding them together.
How to use
- Enter the seconds and strokes for one length.
- Enter your pool length.
- Read the score, and the speed and stroke length underneath it.
- See every other swim that scores the same.
Frequently asked questions
What is SWOLF?
Seconds for a length plus strokes taken. That is the whole formula — a duration added to a tally, which is why the result has no units and cannot be converted into anything else.
Can two different swims score the same?
Many can. Over a 25 m length, SWOLF 40 covers everything from 14 seconds with 26 strokes to 32 seconds with 8 — speeds from 0.78 to 1.79 m/s and stroke lengths from 0.96 to 3.13 m. Same score, opposite swimmers.
So is SWOLF useless?
No, but it is yours alone. Hold the time and it tracks the stroke; hold the stroke and it tracks the speed. Against your own previous scores, same pool and same stroke, a falling SWOLF is real progress.
Can I compare my score with someone else?
Not meaningfully, and not across pools either. The identical swim — same speed, same distance per stroke — scores differently in a 50 m pool than a 25 m one, because both halves of the sum double.
What is the exchange rate between the two halves?
Exactly one stroke per second, which is not a fair trade in any pool. A second is worth far more to a race than a stroke is, so the score treats a real improvement and a real regression as equivalent.
What should I watch instead?
The two numbers underneath it. Distance per stroke is in metres and stroke rate is per minute — both are honest units, both convert, and between them they say everything SWOLF says without the ambiguity of adding them.
How should I count strokes?
However you always count them, and stay consistent. Some swimmers count one arm and some count both. Since the score only means anything against your own history, the convention matters far less than not changing it.
Does this send anything anywhere?
No. Every figure is computed in your browser, and nothing is uploaded or stored.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.