Race Time Predictor
Predict 5K to marathon from one recent result
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Race Time Predictor
One honest race or time trial can predict your times at other distances. Enter the distance you ran and the time it took, and this predictor uses the well-known Riegel formula to estimate your 1500 m, 5K, 10K, 10-mile, half-marathon and marathon times, with the pace per kilometre for each. Predictions assume similar conditions and that you train appropriately for the longer events — they set realistic race targets and pacing.
Uses the Riegel formula (T2 = T1 × (D2/D1)^1.06). Predictions assume similar conditions and appropriate endurance training for the longer distance; without enough long-run preparation, real marathon times are usually slower than predicted.
Frequently Asked Questions
- What is a race time predictor?
- A race time predictor estimates your finish times at other distances from one recent race result. By entering a known time, you can forecast your likely 5K, 10K, half-marathon and marathon performances to help set realistic pacing and goals.
- How accurate is the Riegel race prediction formula?
- Riegel's formula scales time with distance using an endurance exponent of about 1.06. It is most accurate for distances close to your input race and for well-trained runners; predictions for much longer events assume adequate endurance training.
- Why is my predicted marathon time slower than expected?
- Longer races expose endurance and fueling limits that short races do not, so the formula intentionally adds time as distance grows. If your marathon training is strong you may beat the estimate; if undertrained, you may fall short.