How to use it
- Choose the Pool you swam in: its length sets the pace per 100.
- Type one length per line: the time for the length, then the strokes you took for it, for example 0:32 14.
- Read Average SWOLF and Pace per 100, and open Each length for the score of each one.
How SWOLF and the pace are worked out
For each length, SWOLF is the time in seconds plus the strokes for that length. The average SWOLF is the average of those sums. The pace per 100 is the average time for one pool length, multiplied by 100 and divided by the length of the pool in the same unit. A 25-yard pool is a 25-yard length, so 100 yards is four lengths.
SWOLF of one length = seconds + strokes
Average strokes = total strokes ÷ number of lengths
Pace per 100 = average seconds × 100 ÷ pool lengthThe pool lengths
The Wikipedia article on swimming says that World Aquatics recognises the 25 m and 50 m pools for international competitions, and that a 25-yard pool is commonly used for competition in the United States, especially at college level.
What SWOLF is, and what the calculator does not cover
- SWOLF is a swimmers' convention, not a value set by a governing body. The sources used for this page do not define it, so the sum above is the calculator's definition.
- The strokes are the number you count. The calculator takes the number you type for each length.
- The pace is an average over the lengths you type. It is not a race time, and the calculator does not split a set into intervals or rest.
Worked example: six lengths of a 25 m pool
The default set has six lengths: 32 s with 14 strokes, 31 s with 13, 33 s with 14, 30 s with 13, 32 s with 14 and 31 s with 13. The times add to 189 s, so the average is 189 ÷ 6 = 31.5 s. The strokes add to 81, an average of 13.5. The average SWOLF is 31.5 + 13.5 = 45.0.
The pace is 31.5 × 100 ÷ 25 = 126 s, which is 2:06 per 100 m.
| Length | Time (s) | Strokes | SWOLF |
|---|---|---|---|
| 1 | 32.0 | 14 | 46.0 |
| 2 | 31.0 | 13 | 44.0 |
| 3 | 33.0 | 14 | 47.0 |
| 4 | 30.0 | 13 | 43.0 |
| 5 | 32.0 | 14 | 46.0 |
| 6 | 31.0 | 13 | 44.0 |
Frequently asked questions
What is SWOLF?
SWOLF adds the time for one length, in seconds, to the strokes you took for it. A set of lengths gives one SWOLF for each length and an average. The sources used for this calculator do not define SWOLF, so the sum is the calculator's convention.
Why do I type the time and the strokes on one line?
SWOLF needs both numbers for the same length, so the calculator reads each line as one length: the time first, then the strokes.
Which pool length should I choose?
Choose the pool you swam in. The Wikipedia article says the 25 m and 50 m pools are recognised for international competitions, and that a 25-yard pool is commonly used in the United States.
How is the pace per 100 worked out?
The average time for one length, multiplied by 100 and divided by the length of the pool. In a 50 m pool an average of 31.5 s for a length gives 63 s, or 1:03 per 100 m.
Why does the calculator reject a line?
A line must hold exactly two things: the time and the strokes. The strokes must be a whole number from 1 to 200, so decimal strokes and a missing number are refused.
Can I mix metres and yards?
The pool sets the unit: a 25 yd pool gives the pace per 100 yards and the distance in yards. The calculator does not convert between metres and yards.
Sources
Figures and text last checked on Tuesday, November 10, 2026.