Running pace calculator
Distance, time, pace. Fill in any two and the third follows — and it comes back in per-kilometre and per-mile at the same time, because most runners think in one and most races are measured in the other.
This one runs on your own device. It is worked out in your browser, so there is nothing to send and nothing to log. Where a tool on this site does send something out, that page says so and names where it goes.
Why both units, every time
A great many runners train in minutes per kilometre and race distances that are named in miles, or the other way round, and the conversion is not one anybody does in their head mid-run. Eight minutes a mile is 4:58 a kilometre; five minutes a kilometre is 8:03 a mile.
So both are always given, and so are km/h and mph, rather than making you pick a unit before you have seen an answer. A mile is exactly 1.609344 kilometres, so none of those conversions is an approximation.
The race distances are not round numbers
A marathon is 42.195 kilometres and a half is 21.0975. Rounding the marathon to 42 makes a four-hour pace look about a second per kilometre faster than it is, which over the real distance is more than a minute at the finish.
The 5 and the 10 really are 5 and 10. It is the two longer ones that catch people out, and those are the ones people are most likely to be pacing carefully.
Even splits are a plan, not a prediction
The split times below assume you run every kilometre at exactly the same pace. Almost nobody does: hills, wind, the first-mile adrenaline and the last-mile everything all get in the way, and a great many good races are run slightly negative — the second half faster than the first.
What even splits are good for is knowing where you should be. If the plan says 22:30 at halfway and the watch says 21:40, that is information worth having at 10 km rather than at 18.
Where to go next
If you are doing this for a reason rather than out of curiosity:
- calorie calculator — the intake half of the same sum
- BMI calculator — and the measure most people are actually chasing
What this does not do
It is arithmetic, not coaching. It cannot tell you what pace you can hold, what you should be training at, or whether a target is realistic — those depend on you, and no formula on a page knows anything about you.
Nor does it predict a race time from another distance. The formulas that claim to are fitted to other people's results, disagree with each other, and are least reliable exactly where they are most used, which is predicting a first marathon from a 5 km.