Enter one recent race result and we'll predict your times across every common distance — from the mile to the marathon.
| Distance | Predicted time | Pace /km | Pace /mi |
|---|---|---|---|
| 1 mile | 7:31 | 4:40 | 7:31 |
| 5K | 25:00 | 5:00 | 8:03 |
| 10K | 52:07 | 5:13 | 8:23 |
| 15K | 1:20:07 | 5:20 | 8:36 |
| 10 mile | 1:26:19 | 5:22 | 8:38 |
| Half Marathon | 1:55:00 | 5:27 | 8:46 |
| Marathon | 3:59:47 | 5:41 | 9:09 |
Estimates use Riegel's formula (exponent 1.06) and assume you're trained for the target distance.
Choose the distance of a recent race (or pick “Custom” for an unusual one), enter your finish time, and the table updates with equivalent performances across the mile, 5K, 10K, 15K, 10-mile, half marathon, and marathon — each with its goal pace.
In 1981, Peter Riegel published the endurance equation now used by coaches and race-prediction tools everywhere:
T₂ = T₁ × (D₂ / D₁)^1.06
The exponent of 1.06 captures how runners fade as distance grows. If you held the exact same pace at every distance the exponent would be 1.0 — real physiology pushes it slightly higher.
Predictions are a starting point, not a guarantee. Pair them with consistent training and track whether your real times are beating or trailing the model. ActivityStat surfaces your pace and personal records on every Strava activity, making it easy to see whether you're on track for your next goal race.
It uses Peter Riegel's formula: T2 = T1 × (D2 ÷ D1)^1.06, where T1 is your known time over distance D1 and T2 is the predicted time over the new distance D2. The 1.06 exponent accounts for the fact that you slow down slightly as distance increases.
Riegel's formula is a well-established estimate and is most accurate when the predicted distance is reasonably close to your known one, and when you're properly trained for it. Predicting a marathon from a 5K tends to be optimistic because the marathon depends heavily on endurance and fuelling, not just speed.
Use a recent, hard effort over a distance close to your target. To predict a marathon, a recent half marathon gives a far better estimate than a 5K. The fresher and more race-like the effort, the better the prediction.
Longer races are run at a lower percentage of your VO2 max because your body can't sustain high intensity for hours. Fatigue, glycogen depletion, and pacing all compound, which is why a marathon pace is slower than 5K pace — and why the formula uses an exponent above 1.
ActivityStat connects to Strava and writes your pace, power zones, cadence, and performance trends straight into each activity description. Free to start.