Fitness tool
Running Pace Calculator
Calculate running pace, finish time or distance in km or miles, with splits and predicted 5K, 10K, half and full marathon times. Free, nothing stored.
Nothing you enter leaves your device.
Inputs
Results
Enter values to see your results.
Simple steps
How it works
- 01
Choose what to calculate: pace, time or distance.
- 02
Choose km or miles, and enter the two values you know (or pick a race).
- 03
Select Calculate to see your pace, speed, splits and race predictions.
Good to know
Frequently asked questions
How do I enter times?
Use hours, minutes and seconds with colons: 25:30 is 25 minutes 30 seconds, and 1:05:00 is one hour and five minutes. Pace uses minutes and seconds per km or mile, such as 5:30.
What are splits?
The time at which you should pass each kilometre or mile at an even pace. They help you plan a race.
How are race times predicted?
With Riegel's formula: time for a new distance = your time × (new distance ÷ your distance) to the power 1.06. It assumes similar training for both distances.
How accurate are the predictions?
They are best between distances that are not too far apart, such as 10K to half marathon. Marathon predictions from short races are often too fast without long-distance training.
What are the race distances?
5K is 5 km, 10K is 10 km, a half marathon is 21.0975 km and a marathon 42.195 km.
Can I use miles?
Yes. Choose miles and enter distances in miles and pace per mile; both units are shown in the results.
Is anything I enter stored or sent?
No. The calculation runs in your browser. Nothing you type is saved or sent to a server.
How it is calculated
Pace = time ÷ distance; speed = distance ÷ time; 1 mile = 1.609344 km. Splits multiply the pace by each whole km or mile. Race predictions use Riegel's formula: T2 = T1 × (D2 ÷ D1)^1.06.
Sources
- Riegel PS. Athletic records and human endurance. American Scientist 1981;69:285–90
Last reviewed: October 14, 2026