Running Pace Calculator

How it works

Distance, time and pace are all derived from the same two numbers: pace per km is time divided by distance (converting miles to km at 1.609344 km per mile first), pace per mile scales that by the same factor, and average speed is distance divided by time in hours. The race-time table applies Riegel's formula — T2 = T1 × (D2/D1)^1.06 — to project your pace onto five standard distances from one mile to the marathon, a widely-used estimate based on how endurance scales with distance rather than a simple linear pace multiplication.

FAQ

How accurate is the Riegel formula for predicting race times?

It's a reasonable estimate for races run at similar effort, using the exponent 1.06 that Peter Riegel derived from real race data in 1977, but it doesn't account for terrain, weather, or the extra endurance demands of much longer distances — a 5K time won't perfectly predict a marathon time.

Why do the predicted times show 0:00 if I enter 0 for time or distance?

Pace and predictions are both undefined without a real distance and time — the calculator shows 0:00 in those fields rather than guessing, since dividing by zero, or scaling from a zero baseline, has no meaningful result.