How to use the running Pace Calculator
- Enter the distance you ran and choose kilometres, miles or metres.
- Enter your finishing time in hours, minutes and seconds. Leave hours at 0 for runs under an hour.
- The result updates instantly as you type. There is no button to press.
- Use Copy result to copy the figures, or Copy link to share a link that reopens the running Pace Calculator with the same inputs.
How it works
Pace is the time it takes to cover one unit of distance, usually a kilometre or a mile. Runners use pace rather than speed because it maps directly onto a watch and a race plan: if you want to break 50 minutes for 10K, you need to average 5:00 per kilometre. This calculator turns any distance and time into pace per kilometre, pace per mile, speed and lap times for a 400 m track.
It also predicts your finishing times at other distances using Riegel's formula, published by engineer and runner Peter Riegel in 1977. It reflects the fact that you slow down as races get longer: doubling the distance takes slightly more than twice the time. The exponent of 1.06 fits trained runners well from about 1.5 km to the marathon.
Predictions are most reliable between distances that are close together, such as using a 10K to predict a half marathon. Marathon predictions from short races are often optimistic unless you have done the long training runs that marathons need. Heat, hills, wind and race-day fuelling also change real results, so use the predicted times as a starting point for pacing, not a promise.
Formula
T₁ and D₁ are your known time and distance; T₂ is the predicted time for distance D₂. One mile = 1.609344 km. A half marathon is 21.0975 km and a marathon 42.195 km.
Example
A 10 km run in 50:00 is a pace of 3,000 s ÷ 10 = 300 s, or 5:00 per km, which is 8:03 per mile and 12 km/h. Riegel's formula predicts about 23:59 for 5K, 1:50:19 for a half marathon (3,000 × 2.10975^1.06 ≈ 6,619 s) and about 3:50:01 for a marathon.
Frequently asked questions
How do I convert pace per km to pace per mile?
Multiply the pace per kilometre by 1.609. For example, 5:00 per km × 1.609 ≈ 8:03 per mile. To go the other way, divide by 1.609.
How accurate are race time predictions?
They are good estimates for trained runners at similar distances. For the marathon, predictions from short races tend to be optimistic unless your training includes plenty of long runs.
What is a good running pace for beginners?
Many new runners average 6:00–7:30 per km (about 10–12 minutes per mile) on easy runs. Easy runs should feel conversational, whatever the number on the watch.
Disclaimer: This calculator provides general estimates for education only and is not medical advice, diagnosis or treatment. Formulas are based on population averages and may not fit your body, age, pregnancy or health conditions. Talk to a doctor, midwife or registered dietitian before making decisions about your health.