Race time predictor
Enter one recent race. See what that fitness points to at every distance from the mile to the marathon, with a realistic range rather than one magic number.
| Distance | Predicted | Pace /km | Likely range |
|---|
Tap a row to show it on the clock.
Turn this result into a full Race Pace Plan. Tell us your race and goal time. You get one PDF with:
- Goal pace and splits for your race
- Training paces for all five zones
- A printable pace band
How the prediction works
The calculator uses Pete Riegel's formula from 1977, the most widely used model for comparing race performances across distances:
T₂ = T₁ × (D₂ ÷ D₁)kT₁ and D₁ are your race time and distance, D₂ is the distance you want to predict, and k is the fatigue exponent. Riegel's value is 1.06. The range column uses k from 1.04 to 1.08, which covers most recreational runners.
Move the slider left if you hold pace well over long distances, and right if you are fast in short races but fade late.
Common questions
Why is my marathon prediction too optimistic?
Riegel assumes you have trained for the distance. Predicting a marathon from a 5K only works if your weekly volume supports it. Under about 50 km a week, plan for the slow end of the range or slower.
Which race should I enter?
A recent, all-out effort on a flat course, ideally 10K or half marathon. The closer the input distance is to your goal race, the more reliable the prediction.
Is this the same as VDOT?
No. VDOT is a separate system by Jack Daniels. This page uses Riegel's public formula.