Race Time Predictor
Run a 5K PB last weekend? Enter any recent race result and see predicted equivalents from 1500 m to the full marathon.
1500 m6:59
5K25:00
10K52:07
Half1:55:00
Marathon3:59:47
Riegel formula (exponent 1.06). Assumes appropriate training for each distance.
Formula
T2 = T1 × (D2/D1)^1.06 (Riegel)How to use the Race Time Predictor
- 1Enter a recent race distance and time
- 2See predicted times for every standard distance
- 3Remember predictions assume proper training
Frequently Asked Questions
How accurate is the Riegel formula?
It assumes you trained specifically for each distance. Most runners find 10K-to-half reliable but need real endurance work for the marathon prediction to hold.
Why is my marathon prediction faster than I've run?
The formula assumes aerobic development matches your shorter races. If the gap is big, race-pace long runs and more weekly volume close it.