Running Pace Calculator
Pace, speed and finish time over any distance — give the time or give the pace.
Runs entirely in your browser. Nothing is uploaded, logged or stored.
Finish time
45:00
- Pace per kilometre
- 4:30
- Pace per mile
- 7:15
- Speed (km/h)
- 13.33
- Speed (mph)
- 8.28
- Distance
- 10 km
Two of pace, speed and time determine the third once the distance is fixed. Give whichever you have and the rest follow, in both metric and imperial.
How it works
Pace is the reciprocal of speed and nothing more. Four minutes thirty per kilometre is 13.33 km/h, and the two can never disagree — if a calculator shows them disagreeing, one of them is rounded before being used rather than after.
The standard distances are definitions, not measurements. A marathon is 42.195 km because World Athletics defines it so, a half is exactly half of that at 21.0975 km, and the international mile has been exactly 1609.344 m since 1959. None of them will ever change.
Paces are rounded to the second. A pace given to the tenth suggests a precision that neither a runner nor a watch actually has over a whole race.
Examples
| Case | Input | Result |
|---|---|---|
| A 10 km in forty-five minutes | 10k, 45:00 | 4:30 /km, 13.33 km/h |
| Holding that pace over a marathon | marathon at 4:30 /km | 3:09:53 |
| A track distance | 800m, 2:10 | 2:42 /km, 22.15 km/h |
Frequently asked questions
Does a bare number mean kilometres or metres?
Kilometres. A track runner typing 800 means metres and a road runner typing 10 means kilometres, and no rule satisfies both — so the page picks one, says so, and accepts 800m when you mean the other.
Why is my marathon prediction from this pace optimistic?
Because this holds the pace constant, which is arithmetic rather than a prediction. Nobody runs a marathon at their 10 km pace. For a prediction that accounts for the decay, use the race time predictor — it applies a published formula instead.
How do I write a time?
45:00 is forty-five minutes and 3:30:00 is three and a half hours. A bare number is minutes. The same convention is used everywhere on this site.
Good to know
- Everything here is exact arithmetic on the distance you gave. It makes no claim about whether you can hold the pace — that is the one question a calculator cannot answer.