Race Predictor
Enter a recent race finish time to see predictions for other distances, from 1500 m to a marathon. Results are shown as an estimated range, not a certainty.
Equivalent pace: 4:00 /km
From 5K 20:00 · 10K 41:42 · 41:25–42:17
ExamplePredicted 10K 41:42
Equivalent race predictions
| Distance | Predicted Time / Range | Pace /km |
|---|---|---|
| 1500m | 5:355:27–5:39 | 3:43 |
| Mile | 6:015:53–6:05 | 3:44 |
| 5K | 20:00 | 4:00 |
| 5 Mi | 33:0732:58–33:26 | 4:07 |
| 8K | 32:5532:46–33:14 | 4:07 |
| 10K | 41:4241:25–42:17 | 4:10 |
| 15K | 1:04:051:03:23–1:05:31 | 4:16 |
| 10 Mi | 1:09:031:08:15–1:10:41 | 4:17 |
| Half Marathon | 1:32:001:30:41–1:34:42 | 4:22 |
| 30K | 2:13:372:11:15–2:18:30 | 4:27 |
| Marathon | 3:11:493:07:46–3:20:11 | 4:33 |
How it works
Choose the distance you raced and enter your time: for example, 5K in 20:00 predicts a 10K of about 41:42. For 5 mi, 8K, 10K and longer distances, you can use hours, minutes and seconds. Each row shows the central prediction and the model’s range.
What to keep in mind
This is a mathematical prediction, not a performance guarantee. It assumes you have developed the required endurance and trained appropriately for the target distance. The model’s range reflects different assumptions about performance decline as distance increases; it is not your personal probability of success. For marathons, the Riegel model tends to be optimistic for many recreational runners: in the Vickers & Vertosick study, around half finished at least 10′ slower than predicted.
Methodology & sources
Model: the Riegel equation, T₂ = T₁ × (D₂ / D₁)ᵏ. The central prediction uses k = 1.06 and the displayed range uses k = 1.05–1.08. This is a range of model assumptions, not a statistical confidence interval. The equation is used for efforts of approximately 3.5–230 minutes. For the marathon, the discrepancy observed in recreational runners by Vickers & Vertosick is taken into account. Exact distances are used, including half marathon 21.0975 km and marathon 42.195 km. Display is rounded to the nearest second.
https://pubmed.ncbi.nlm.nih.gov/27570626/
Last updated: 6 July 2026
A prediction still needs the right preparation.
The prediction comes from a formula. Achieving the goal requires appropriate training, sound pacing and a tested fuelling strategy. We organise these together through 1:1 coaching.