Race Time Predictor
Predict race times from a recent result.
Reviewed by James Whitfield · How we check our maths
Your values
ⓘ Live results
Results
- Predicted marathon
- 3:33:55
- Predicted half marathon
- 1:42:36
- Predicted 10K
- 46:30
- Predicted 5K
- 22:18
- Predicted mile
- 6:42
- Current pace
- 4:39 per km
| Distance | Predicted time |
|---|---|
| 1 mile | 6:42 |
| 5K | 22:18 |
| 10K | 46:30 |
| Half marathon | 1:42:36 |
| Marathon | 3:33:55 |
Quick answer
Riegel's formula predicts race time as T₂ = T₁ × (D₂/D₁)^1.06 across distances.
The formula
T₂ = T₁ × (D₂ ÷ D₁)^1.06
Worked example
Worked example
Using the values the calculator loads with.
Inputs
- Recent race distance10 km
- Hours0
- Minutes46
- Seconds30
Result
- Predicted marathon3:33:55
- Predicted half marathon1:42:36
- Predicted 10K46:30
- Predicted 5K22:18
- Predicted mile6:42
- Current pace4:39 per km
How to use the Race Time Predictor
- 1Enter the distance of a recent race in kilometres.
- 2Enter your finishing time.
- 3Read predicted times for other distances.
Frequently asked questions
How accurate is Riegel's formula?
Good within a factor of about 3× in distance. Marathon predictions from a 5K tend to be optimistic without marathon-specific training.
Why the 1.06 exponent?
It reflects the empirical slowdown as distance grows; well-trained endurance runners are closer to 1.05.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error