How to use the pace calculator
- Choose what to calculate: your pace, your finish time or the distance.
- Enter the other two values. Tap 5K, 10K, half marathon or marathon to fill in race distances.
- Type times as h:mm:ss or mm:ss (for example 1:45:00 or 24:30) and paces as min:sec.
- Read the pace per kilometre and mile, speed, predicted race times and kilometre or mile splits.
Pace, speed and predicting race times
Pace is time per distance, the way runners usually think: a 50-minute 10K is a pace of 5:00 per kilometre, or 8:03 per mile, which equals 12 km/h. Speed is the inverse, distance per hour, more common for cycling.
The race predictor uses Peter Riegel's formula, published in 1977 and still the standard in running calculators: T2 = T1 × (D2 ÷ D1)1.06. The exponent of 1.06 reflects that pace slows as distance increases. It works best when the race you base it on is recent, run all-out, and not too different in length from the target. Predictions for the marathon from a 5K are usually optimistic unless you have done the long-distance training; most runners finish 5–10% slower than predicted on their first marathon.
Use the splits table to plan an even-paced race, or write a few key splits on your wrist. Everything is calculated in your browser.
What is a good 5K time?
For recreational runners, 25–30 minutes is common; under 20 minutes is fast. Age and experience matter a lot.
How accurate is the Riegel formula?
Usually within a few percent for distances from 1.5 km to the half marathon, if you are trained for the target race.
Can I use it for cycling or swimming?
The pace and speed maths work for any sport; the race predictions are calibrated for running.