Pace & Speed Converter
How it works
Pace and speed are the same measurement inverted: one is time over distance, the other distance over time. That inversion is where converters go wrong, so every figure entered here is turned into one internal basis first — seconds per kilometre — and every readout comes back out of it. Holding a pace in whole seconds is what makes 5:30/km come back as 5:30 rather than as 5:29 from an accumulated 5.4999 minutes.
Finish times are that basis multiplied by the distance, at the official race distances: 5 km, 10 km, 21.0975 km and 42.195 km. They assume an even pace the whole way, which is the arithmetic rather than a prediction — most runners lose time in the second half of a long race.
Frequently asked questions
What is the difference between pace and speed?
They are the same thing upside down. Pace is time over distance, so a bigger number is slower — 6:00/km is slower than 5:00/km. Speed is distance over time, so a bigger number is faster. 5:00/km and 12 km/h are the same runner.
Why is my mile pace a bigger number than my km pace?
A mile is 1.609344 km, so it takes longer to run one. A 5:00/km pace is 8:03/mile. The mile figure is the km figure multiplied by 1.609344 — the mph figure, going the other way, is smaller than km/h for exactly the same reason.
Are the race projections realistic?
They are arithmetic, not predictions: this is what an even pace held the whole way produces. Real marathons drift slower in the second half, and the distances used are the official ones — 21.0975 km and 42.195 km, not 21.1 and 42.2.