What marathon time, based on your 10K?
Enter the time from a recent race and the tool estimates what you can aim for over 5K, 10K, half marathon and marathon. Then get ready for the one you want.
Your estimated times
| Race | Time | Pace | Target this time |
|---|---|---|---|
| 5K | 23:59 | 4:48 /km | Target this time |
| 10 km | 50:00your time | 5:00 /km | |
| Half marathon | 1:50:19 | 5:14 /km | Target this time |
| Marathon | 3:50:01 | 5:27 /km | Target this time |
How it's calculated
The Riegel formula.
Peter Riegel, an engineer and marathoner, noticed in 1977 that time rises slightly faster than distance: t₂ = t₁ × (d₂ / d₁)^1.06. Doubling the distance doesn't double your time, it multiplies it by about 2.08.
It's the same formula your coach uses to read your level from your personal bests: the times estimated here are the ones your training plan would be built on.
It assumes you're trained for the target distance. For a marathon, endurance counts as much as speed: without long runs, the estimated time is a ceiling, not a promise. The closer your reference race is to your target race, the more accurate the estimate.
Questions
What you ask us.
- How accurate is the time prediction?
- Within a few minutes between two close distances, as long as you're trained for the longer one. From a 5K, the estimated marathon time is often too optimistic.
- Which time should I enter?
- One from a recent race, less than three months old, run all-out on a flat course. A workout or a race where you held back will skew the estimate.
- How do I hit the predicted time?
- With training tailored to the distance: your coach builds your plan up to race day, based on your level, and adjusts it every week.
Your predicted time, now your plan.
Watch or not, all you need is a phone number.
Training plansMarathon planHalf marathon plan