The formula
Pace per 100 m = total time ÷ (distance ÷ 100)
Where it comes from
Swimming measures pace every 100 metres for a practical reason: it is the distance of most training sets and it fits into four lengths of a short-course pool or two of an Olympic one. A "1:30 per 100" means a minute and a half for every hundred metres, and a whole session can be planned from that single figure. Speed in metres per second is useful for comparing with other sports; pace per 100 is what you swim to.
How to work it out by hand
- Turn the total time into seconds: minutes times 60, plus the seconds
- Divide the distance by 100 to get the number of hundred-metre stretches
- Divide the total time by those stretches
- Convert the result back into minutes and seconds
What is worth knowing
The table below projects your pace onto other distances assuming you hold it, which makes it a reference rather than a forecast: in water, drag grows with the square of speed, so almost nobody sustains over 1,500 metres the pace they hit over 100. What the projection does reveal is the opposite, and it is more useful: if your 100 pace projects a 1,500 faster than you have ever swum, the problem is not endurance, it is that you go out too hard. Always compare paces over the same distance, and bear in mind that a short-course pool gives better times because every turn hands you a push.