Running Pace Calculator

What does this calculate?

Your pace from a distance and a time: total seconds divided by distance, reported both as minutes per kilometre and minutes per mile. Enter the distance in whichever unit you prefer — miles are converted at 1.609344 km before the division.

Which race distances are built in?

5K, 10K, half marathon at 21.0975 km and marathon at 42.195 km. Those are the official distances, which is why the last two are not the round 21 and 42 that people usually say out loud — over a marathon, that 0.195 km is most of a minute for many runners.

What is the difference between pace and speed?

They are inverses of the same thing. Pace is time per unit distance (5:00 per km); speed is distance per unit time (12 km/h). Runners generally think in pace because it maps directly onto what a watch shows during a run, while cyclists tend to think in speed.

Why does my watch show a different pace than this?

A watch reports instantaneous or rolling-average pace and estimates distance from GPS, which drifts under tree cover, between tall buildings and on sharp turns. This calculator gives the exact average across the distance you enter. If your watch measured 5.08 km on a 5.00 km course, its pace will read slightly faster than reality.

Can I use it to work out a target finish time?

Yes — that is the same equation rearranged. Put in the race distance and the pace you can hold, and the tool gives the finishing time. Just remember that holding a pace for 5 km and holding it for a marathon are entirely different propositions; a pace you can sustain gets slower as distance grows.

Why do my splits vary so much on the same route?

Terrain and effort distribution, mostly. Elevation, wind, heat and surface all change what a given effort produces, so an even-pace run and an even-effort run are not the same run. Comparing like-for-like means comparing the same route in similar conditions.

Does it handle hours as well as minutes?

Yes. Times over an hour are formatted with hours, minutes and seconds; shorter ones show minutes and seconds. Pace itself is always shown as minutes and seconds per unit.

Is anything sent to a server?

No. The arithmetic runs entirely in your browser.