Running pace calculator
Your pace per kilometre and per mile, the splits for every common race distance, and an honest prediction of what that pace means over further.
Your pace
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| Pace per km | — |
|---|---|
| Pace per mile | — |
| Speed | — |
| Predicted 5K | — |
| Predicted 10K | — |
| Predicted half marathon | — |
| Predicted marathon | — |
Pace, speed and why runners use pace
Speed answers "how fast" and pace answers "how long will this take" — which is the question you actually have at kilometre 8. Pace is minutes per kilometre or per mile, and it is the number that translates directly into a finish time and into a plan you can hold.
How far the predictions can be trusted
The Riegel formula scales your time by the ratio of distances raised to the power 1.06. That exponent is doing the important work: it says you get slower as distance grows, and by roughly how much. Doubling the distance costs about 7% on pace, not zero.
It holds up well within a factor of about three — a 10K predicts a 5K and a half marathon decently. Predicting a marathon from a 5K is where it breaks down, and it breaks down optimistically. The formula assumes you have trained the endurance to hold that shape, and the marathon is precisely the distance where an untrained aerobic base stops being hideable. If you have not run beyond 25km in training, treat the marathon prediction as a ceiling you will not reach rather than a target.
Common race pace reference
| Pace /km | 5K | 10K | Half | Marathon |
|---|---|---|---|---|
| 4:00 | 20:00 | 41:41 | 1:32:30 | 3:12:34 |
| 5:00 | 25:00 | 52:07 | 1:55:38 | 4:00:43 |
| 6:00 | 30:00 | 62:32 | 2:18:45 | 4:48:51 |
| 7:00 | 35:00 | 72:57 | 2:41:53 | 5:37:00 |
Marathon figures assume even pacing, which almost nobody achieves. Most runners slow in the second half; a negative split is rare enough to be remarked on.
Common questions
How do I calculate running pace?
Divide your total time by the distance. For minutes per kilometre, take the time in seconds, divide by the kilometres, then convert back to minutes and seconds.
How accurate are race time predictions?
Reasonably good within about three times the distance you ran, using the Riegel formula. Predicting a marathon from a 5K is systematically optimistic because it assumes endurance you may not have trained.
What is a good 5K time?
It depends entirely on age, training and history. Around 30 minutes is a common first-timer target and roughly 25 minutes is a frequent milestone for regular recreational runners. Comparing to your own previous times is more useful than to anyone else.
What pace do I need for a sub-4-hour marathon?
About 5:41 per kilometre, or 9:09 per mile, held evenly for the whole distance. In practice most runners aim slightly faster early to allow for slowing later.
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