SWOLF is the time in seconds plus the stroke count for one pool length. Use it to compare similar swims in the same pool length and stroke. A lower score alone does not prove that you swam faster, used less energy, or improved your technique.
How to calculate SWOLF
SWOLF = seconds per length + strokes per length. For example, a length taking 25 seconds and 18 recorded strokes has a SWOLF of 43. Apple describes the formula in its watchOS 9 swimming update.
The examples below illustrate the arithmetic; they are not results from a device accuracy test. Use the stroke count reported by the same device or method when comparing scores.
| Repeat | Time | Strokes | SWOLF |
|---|---|---|---|
| A | 25 seconds | 18 | 43 |
| B | 24 seconds | 18 | 42 |
| C | 27 seconds | 15 | 42 |
Repeat B is faster than A with the same stroke count. Repeat C has the same SWOLF as B but takes three seconds longer. That is why you need the time and stroke count alongside the score.
What is a good SWOLF score?
There is no single target that works across swimmers, strokes, and pool lengths. A 50-meter length requires a different amount of swimming from a 25-meter length, so their scores are not directly comparable. Build a baseline from your own similar sets instead of chasing a universal range.
How to use SWOLF in a training log
- Choose the same pool length, stroke, and repeat distance for comparison.
- Record repeat time, stroke count, SWOLF, rest, and how hard the set felt.
- Compare several similar repeats rather than selecting the lowest score.
- When trying a technique change, check whether the time and effort also support the result.
If fewer strokes make you slower, the lower count may not serve your goal. For a pace-focused set, compare repeat times first and use SWOLF to describe how the stroke count changed.
Why did the score suddenly jump?
Check the underlying length record before treating a jump as a technique problem. Look for missing lengths, interrupted swimming, a stroke change, or a different pool setting. Use the accuracy checklist when distance or length times look wrong.
For a set-level average, check which lengths the watch grouped together. Auto Sets can help you interpret that grouping. The swimming data guide explains how to read pace and other metrics alongside SWOLF.