Running Pace Calculator
Turn a distance and a finish time into pace per kilometre and per mile, plus predicted 5K, 10K, half and full marathon times.
Private ● Runs entirely in your browser Your text never leaves your device.No account required.No data uploaded.Nothing stored unless you choose to save it.Add to Home Screen
Install Running Pace Calculator so it opens like an app and works offline.
- Open Chrome’s menu (⋮, top-right).
- Tap Install app or Add to Home screen.
- Confirm — the icon appears on your home screen.
- Tap the Share button in Safari’s toolbar.
- Choose Add to Home Screen.
- Tap Add.
Enter how far you ran and how long it took to see your pace, speed, and predicted race times.
Timeline
Milestones
Comparison
Assumptions
How this is calculated
Questions to explore
What to do next
Common Questions
How do I calculate running pace?
Divide your total time by the distance. For example, 5 km in 25 minutes is 1,500 seconds over 5, which is 300 seconds or 5:00 per kilometre. In miles that same run is 8:03 per mile, because a mile is 1.609 km. The calculator does both at once, so a run logged in kilometres still gives you the mile pace a race in the United States will be run at.
What is the difference between pace and speed?
They are the same relationship read in opposite directions. Pace is time per distance, written as minutes and seconds per kilometre or mile, and lower is faster. Speed is distance per time, written in km/h or mph, and higher is faster. Runners think in pace because a race target is a time; treadmills and cyclists use speed. For example, 5:00 per kilometre is 12 km/h.
Can a 5K time predict my marathon time?
It can point at a range, but treat it loosely. Riegel's model is most trustworthy within about a factor of three of the distance you ran, so a 5K predicts a 10K well and a half marathon acceptably. A marathon is more than eight times the distance, and the prediction assumes marathon-specific training you may not have done. Runners without a long-run base routinely finish 20 to 30 minutes behind the predicted time.
What is a good 5K pace?
Good is relative to where you started, but some rough markers help. A 30 minute 5K is 6:00 per kilometre and is a solid recreational time; 25 minutes is 5:00 per kilometre and puts you ahead of most club beginners; under 20 minutes, at 4:00 per kilometre, is competitive club running. Improvement in your own times over a season matters far more than any of these.
Why does the predicted pace get slower for longer races?
Because holding a speed gets harder the longer you hold it, and Riegel encodes that in the exponent 1.06. If pace were constant the exponent would be 1, and doubling the distance would exactly double the time. At 1.06 doubling the distance multiplies time by about 2.08, which is the few percent of slowdown real runners show. It is a small number with a large effect over a marathon.
Do hills and terrain change the prediction?
Yes, and the model does not know about them. It assumes flat ground and even pacing throughout. A time set on a downhill course or with a strong tailwind flatters every prediction that follows, and a hilly trail run understates your road form. Feed it a flat, honestly paced effort, ideally a race or a proper time trial, and the numbers behave much better.