Enter any two of distance, time and pace, and this tool works out the third. Find your pace after a run, predict a race finish time from a target pace, or see how far a training pace takes you in a set time. Pace is shown per kilometre and per mile, with speed alongside — all calculated in your browser.
Enter two values to calculate the third.
How it works
The three quantities are linked by one relationship: pace is time divided by distance, and speed is its inverse. Give the tool two of them and it rearranges the formula for the third — distance × pace = time, time ÷ pace = distance, time ÷ distance = pace.
Distances can be entered in kilometres or miles, and the result always shows pace both per km and per mile so you can read whichever your watch uses. Speed is given in km/h and mph. Times use hours, minutes and seconds; pace uses minutes and seconds per unit — the familiar 5:30 style.
A mile is exactly 1.609344 km, and the tool converts internally through kilometres, so switching units never loses precision. Pace and duration are rounded to the nearest second for display, which is why a back-and-forth conversion can differ by a second.
Practical examples
Pace after a 10K
Choose “find pace”, enter 10 km and a time of 50:00. The pace is 5:00 per km (about 8:03 per mile) and the speed is 12 km/h — the numbers to log in your training diary.
Predicting a half-marathon time
Choose “find time”, enter 21.1 km and a target pace of 5:30 per km. The tool returns a finish time of about 1:56:03 — a realistic goal to pace yourself against on race day.
How far in 45 minutes
Choose “find distance”, enter a time of 45:00 and an easy pace of 6:00 per km. That is 7.5 km — handy for planning a lunchtime run to a fixed schedule.
Frequently asked questions
What is running pace?
Pace is how long it takes to cover one unit of distance — for example 5:30 per kilometre means each kilometre takes five and a half minutes. It is the inverse of speed and is how most runners think about effort.
How is pace different from speed?
They describe the same thing from opposite directions. Speed is distance per hour (12 km/h); pace is time per distance (5:00 per km). Runners usually use pace; cyclists and cars usually use speed. This tool shows both.
Can I switch between kilometres and miles?
Yes. Pick the unit for your distance, and the results always list pace per km and per mile plus speed in km/h and mph, so you can read whatever your watch or race uses.
How do I convert min/km to min/mile?
Multiply your per-km pace by 1.609. A 5:00/km pace is about 8:03/mile. The tool does this automatically — both are shown at once.
How do I enter a time under an hour?
Leave the hours field at zero and fill minutes and seconds. For a 50-minute run, enter 0 hours, 50 minutes, 0 seconds; the display drops the hours when there are none.
Is the predicted race time accurate?
It assumes you hold the entered pace evenly for the whole distance. Real races slow over longer distances due to fatigue, so treat a prediction as an even-effort target, not a guarantee — longer races usually finish a bit slower than a flat extrapolation.
What are typical paces to aim for?
That is personal and depends on fitness and terrain. An easy conversational run for many people sits around 6:00–7:00/km, while race paces are faster. Use your own recent runs as the baseline rather than a generic target.
Does it account for hills or intervals?
No. It computes an average pace over the whole distance. For hilly routes or interval sessions the average hides the variation, so pair it with the splits from your watch for a fuller picture.
Is anything I enter stored?
No. The calculation runs entirely in your browser and nothing is uploaded or saved. Reload the page and it resets.
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