Long-distance predictions are optimistic without long-run training.
How running pace works
Pace is the time it takes to cover one kilometre or one mile. It is the number runners use to plan races and training because it maps directly to what a watch shows mid-run. Pace equals time divided by distance, so a 10 km run in 50 minutes is 5:00 per kilometre. To convert between units, multiply a per-kilometre pace by 1.609 to get the per-mile pace: 5:00 per km becomes 8:03 per mile. PaceMath solves any of the three values from the other two. Pick what you want to solve for and type the rest.
Splits
The split table shows where you should be at every kilometre or mile if you run an even pace. Even pacing, or a slightly faster second half, is usually the fastest way to race, especially over long distances. Starting too fast uses up energy you will miss later. Many runners copy splits to a pace band or set the target pace in their watch.
Predicting race times
The predictor uses the formula published by Pete Riegel in 1977: T2 = T1 × (D2 ÷ D1)^1.06. The exponent above 1 accounts for slowing down as races get longer. It works well between similar distances when you have trained for both. For the marathon, it often predicts a few minutes too fast for runners without much weekly mileage, so treat it as a best case.
Treadmill speeds
Treadmills display speed in miles or kilometres per hour. Pace is 60 divided by speed: 6 mph is 10 minutes per mile and 12 km/h is 5 minutes per kilometre. The chart lists common settings in whichever unit you choose. Everything is calculated in your browser.
Frequently asked questions
How accurate is the Riegel formula?
Good for 5K to half marathon; marathon predictions are often a few minutes fast.
Which result should I use?
A recent all-out race close to the target distance.
Does it account for hills or heat?
No. It assumes similar conditions.
Is PaceMath free?
Yes, with no sign-up or ads.
Are my runs saved?
Your last entry is saved in this browser only.