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Pace Calculator
Work out running pace, finish time or distance in km or miles, with 5K, 10K, half and full marathon presets, splits and race time predictions.
Enter any two of distance, time and pace, and the pace calculator works out the third. It shows your pace per kilometre and per mile, your speed in km/h and mph, the split time at every kilometre or mile, and predicted times for the 5K, 10K, half marathon and marathon based on your result.
Use it to plan a race goal, to check how fast you need to run for a personal best, or to convert a treadmill speed into a pace. Choose kilometres or miles; race presets fill in the exact distances.
How to use Pace Calculator
- Choose what to calculate: pace, finish time or distance.
- Choose kilometres or miles and pick a race or enter a distance.
- Enter the time as h:mm:ss or mm:ss, or the pace as m:ss.
- Read the result, the splits and the race predictions.
Features
- Pace, finish time or distance from the other two
- Kilometres or miles, with pace shown in both
- 5K, 10K, half marathon and marathon presets
- Speed in km/h and mph
- Split times for every kilometre or mile
- Race time predictions with Riegel's formula
How pace is calculated
Pace is the time it takes to cover one kilometre or one mile: the total time divided by the distance. A 10K run in 50 minutes is 3,000 seconds over 10 km, a pace of 5:00 per kilometre. One mile is 1.609344 km, so the same pace is 8:03 per mile, and the speed is 12 km/h or 7.46 mph.
Finish time is pace multiplied by distance, so a 5:00 per km pace over the marathon distance of 42.195 km finishes in about 3:30:59.
| Goal | Pace per km | Pace per mile |
|---|---|---|
| 5K in 30:00 | 6:00 | 9:39 |
| 10K in 50:00 | 5:00 | 8:03 |
| Half marathon in 2:00:00 | 5:41 | 9:09 |
| Marathon in 4:00:00 | 5:41 | 9:09 |
| Marathon in 3:30:59 | 5:00 | 8:03 |
Race time predictions
The predictions use Riegel's formula, T2 = T1 × (D2 ÷ D1)^1.06, which scales a race time to another distance while allowing for the fact that you slow down as the distance grows. From a 5K in 25:00 it predicts about 52:07 for 10K, 1:55:00 for the half marathon and 3:59:47 for the marathon.
The formula works best between similar distances and assumes you have trained for the longer race. Marathon predictions from a short race are often too optimistic, especially for newer runners, so treat them as a best case.
Using splits
The splits table shows the time on the clock at every kilometre or mile if you run an even pace. Write down a few of them or put them on a wristband to check during a race. Most coaches suggest an even or slightly negative split, running the second half a little faster than the first, rather than starting fast and fading.
Training paces
Not every run should be at race pace. Easy runs are usually one to two minutes per kilometre slower than your 5K pace, tempo runs close to the pace you could hold for an hour, and intervals faster than 5K pace. Use the calculator to turn a target time into a pace, then plan training around it.
Treadmill speed and pace
Treadmills usually show speed rather than pace. Divide 60 by the speed in km/h to get minutes per kilometre: 10 km/h is 6:00 per km and 12 km/h is 5:00 per km. In the calculator, choose Pace, enter any distance and the time it takes at that speed, and read the pace and the speed in both units. Running on a treadmill is slightly easier than running outdoors because there is no wind and the belt helps your stride, so many runners set a 1% incline to match outdoor effort.
Frequently asked questions
How do I calculate running pace?
Divide the total time by the distance. 50 minutes for 10 km is 5:00 per km, which is 8:03 per mile.
What pace do I need for a 4-hour marathon?
About 5:41 per km or 9:09 per mile, run evenly over 42.195 km.
How long is a half marathon?
21.0975 km or 13.1 miles. A marathon is 42.195 km or 26.2 miles.
How accurate are the race predictions?
They use Riegel's formula and are a good guide between similar distances. Predictions for the marathon from a short race are usually optimistic.
How do I enter the time?
As h:mm:ss or mm:ss, for example 1:45:30 or 25:00. A single number is read as minutes.
Is my data saved?
No. Everything is calculated in your browser.
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