Running Pace Calculator.
Work out pace, time or distance from the other two, and see predicted finish times for standard race distances.
Predicted finish times at this fitness
Predictions use Riegel’s formula and assume you have trained for the distance. They are optimistic for the marathon if your longest runs are short.
Runs entirely in your browser. The values you enter never leave your device — there is no request to our server and nothing is stored. How we handle data
Pace, Time and Distance
All three are the same relationship rearranged. Fix any two and the third follows. The one thing that trips people up is that pace is written in minutes and seconds, not decimal minutes — 8:30 per mile is 8.5 decimal minutes, not 8.3.
Formula
Time = Pace × Distance
Distance = Time ÷ Pace
How Race Prediction Works
The predicted times come from a formula published by Pete Riegel in 1977 and still the most widely used model in endurance running:
The exponent 1.06 encodes a simple observation: doubling the distance costs slightly more than doubling the time, because you cannot hold the same intensity for longer. If the exponent were 1.0, a 20-minute 5K would predict a 40-minute 10K. In practice it predicts about 41:40, and that extra 100 seconds is the fatigue penalty.
The model has a real limitation worth knowing. It assumes you are trained for the target distance. A runner with a sharp 5K time who has never run further than 10 miles will not hit the predicted marathon time, because the marathon is limited by endurance and fuelling rather than by speed. Treat the 5K and 10K figures as reliable, and the marathon figure as a ceiling you have to earn with long runs.
Using Pace in Training
Easy pace
Roughly 1:30–2:00 per mile slower than 10K pace. Should feel conversational. Most distance runners do the large majority of their weekly mileage here, and running it too fast is the most common training error.
Threshold pace
Close to the pace you could hold for about an hour of hard racing — near 10-mile to half marathon pace for most runners. Comfortably hard: sustainable, but not conversational.
Interval pace
Around 3K to 5K race pace, run in repetitions with recovery between. Used to raise aerobic ceiling rather than endurance.
Internal Navigation
Running Pace, Race Times and What They Mean Methodology.
The Calculation Branch
Industrial Standards.
Pace conversion is exact arithmetic. Race-time prediction uses Pete Riegel's 1977 endurance formula with the standard exponent of 1.06, which models the observed rate at which sustainable intensity falls as race distance grows. Distances follow official measurements: a marathon is 42.195 km and a half marathon 21.0975 km.
In-Depth Analysis & Reference Data
One practical note on unit switching: a pace in minutes per mile and the same effort in minutes per kilometre are not interchangeable numbers, and confusing them is a common cause of badly paced races abroad. An 8:00 mile is roughly a 4:58 kilometre. If your watch is set to one unit and the course is marked in the other, decide which you are racing by before the start.
For a rough conversion in your head, a per-mile pace is about 1.6 times the per-kilometre pace. Runners often work the other way and divide, which produces a pace that feels impossibly fast for the first few kilometres and then falls apart.
Registry Questions & FAQ.
Why is my predicted marathon time so much faster than my actual one?
Riegel's formula assumes equivalent training for both distances. Marathon performance depends heavily on weekly mileage, long-run length and fuelling — none of which a 5K time measures. If your predicted time looks far out of reach, the usual cause is training volume rather than speed.
Should I train by pace or by heart rate?
Pace is precise on flat ground in good conditions. Heart rate adapts better to hills, heat and fatigue, where holding a fixed pace forces a harder effort than intended. Many runners use pace for structured sessions and effort or heart rate for easy running.
Estimates for planning. Always confirm against an authoritative source.