Riegel formula
T₂ = T₁ × (D₂ ÷ D₁)^1.06. The exponent 1.06 reflects that pace slows a little as the distance grows.
Example
A 5 km in 25:00 (5:00 per km, 8:03 per mile) predicts about 52:07 for 10 km, 1:55:00 for a half marathon and 3:59:47 for a marathon.
Use it wisely
- Predictions assume you trained for the longer distance, especially long runs.
- The closer the two distances, the better the estimate: use a half marathon to predict a marathon.
- Heat, hills and wind slow you down.
To turn a time into a pace, use the pace calculator.
Frequently asked questions
Why is my marathon prediction too fast?
Most runners slow down more than the formula expects in the marathon, unless they have done enough long runs.
Does it work for walking?
It works best for running. For walking, the pace changes less with distance.
See also
Results are estimates for information only and are not financial, legal or medical advice. Rates, taxes and fees vary — confirm with a professional or your lender.