Find your pace and speed from any run, then predict your finish time for other race distances.
Based on the Riegel formula, which predicts how race times scale across distances for a trained runner at consistent effort.
| Distance | Predicted Time |
|---|---|
| 5K | 0:00 |
| 10K | 0:00 |
| Half Marathon | 0:00 |
| Marathon | 0:00 |
The Riegel formula assumes your endurance scales predictably with distance, which holds reasonably well for trained runners but breaks down at the extremes — predicting a marathon time from a single mile time run flat-out, for example, will be wildly optimistic, since marathon performance depends heavily on endurance and fueling strategy that a fast mile doesn't test at all. Predictions from a 5K or 10K time toward a half or full marathon tend to be the most reliable use case.
Runners almost universally think in pace (minutes per mile/km), since it directly answers "how do I need to run to hit my goal time." Cyclists and some race directors use speed (mph/kph) instead. This calculator shows both so you're not stuck converting manually.
Race-day factors the formula can't account for — weather, course terrain/elevation, fueling, pacing strategy, and tapering — all affect actual performance. Treat predictions as a rough target, not a guarantee, and adjust your race strategy based on how you're actually feeling on the day.
This depends entirely on your goals, age, and experience level — there's no universal benchmark. A more useful question is whether your pace is improving relative to your own past performances at the same distance and effort level.
The pace and speed math works the same, but the race-distance predictions assume roughly similar terrain and conditions across distances, which rarely holds true on trails with varying elevation and surface. Treat trail predictions as rougher estimates than road predictions. Training for a triathlon? Work out your swim leg with our Swim Pace Calculator.