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Race converter5 km to marathon time converter
Your marathon prediction is roughly 9.51× your 5 km (parkrun) time: a 26:00 points to about 4:07:08, if you train for the longer race. A parkrun is the most common race people have, and the least reliable one to predict a marathon from: it tests speed, and the marathon tests everything else.
| Distance | Predicted time | Pace |
|---|---|---|
| 5 km | 26:00 | 5:12/km |
| 10 km | 53:59 | 5:24/km |
| 15 km | 1:23:11 | 5:33/km |
| Half marathon | 1:59:42 | 5:40/km |
| Marathon | 4:07:08 | 5:51/km |
| Two Oceans 56 km * | 5:51:03 | 6:16/km |
| Comrades (about 90 km) * | 10:32:14 | 7:01/km |
Flat course, good conditions, properly trained for the distance. * Past the marathon, times follow how real Two Oceans and Comrades fields finish (about 1.42× and 2.56× a marathon), not the pure fitness model.
The chart
| 5 km (parkrun) | Marathon (VDOT) | Riegel | Pace |
|---|---|---|---|
| 18:00 | 2:52:25 | 2:52:38 | 4:05/km |
| 20:00 | 3:11:17 | 3:11:49 | 4:32/km |
| 22:00 | 3:30:03 | 3:31:00 | 4:59/km |
| 24:00 | 3:48:40 | 3:50:11 | 5:25/km |
| 25:00 | 3:57:55 | 3:59:47 | 5:38/km |
| 26:00 | 4:07:08 | 4:09:22 | 5:51/km |
| 28:00 | 4:25:28 | 4:28:33 | 6:17/km |
| 30:00 | 4:43:39 | 4:47:44 | 6:43/km |
| 32:00 | 5:01:42 | 5:06:55 | 7:09/km |
| 35:00 | 5:28:30 | 5:35:41 | 7:47/km |
Two formulas, one answer
The VDOT column is Jack Daniels’ model, the same one that sets every Race Shape plan. The Riegel column is Pete Riegel’s 1977 formula, T₂ = T₁ × (D₂/D₁)^1.06, which most online calculators use. For a 26:00 5 km (parkrun) they give 4:07:08 and 4:09:22. When two independent models agree to within a few minutes, the estimate is about as good as a formula gets.
When the prediction is wrong
Over 42.2 km the limit is rarely the engine a parkrun measures. It is fuel, the long run and pacing discipline. Treat the prediction as what your fitness is worth after a full marathon block, not on the current one.
At altitude, add the correction on top: a race at Johannesburg’s height is about 8% slower for the same effort — see the altitude pace calculator.
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Common questions
How do I convert a 5 km (parkrun) time to a marathon time?
Multiply by about 9.51, or use the chart: a 26:00 points to about 4:07:08.
What marathon can I run off a 20:00 5 km (parkrun)?
About 3:11:17 by Daniels’ model, 3:11:49 by Riegel’s, if you train for the marathon.
Which is more accurate, VDOT or Riegel?
They agree closely over these distances. VDOT is slightly more conservative for slower runners; neither knows how much long-run training you have done, which matters more than the formula.
Why did I run slower than my predicted marathon?
Over 42.2 km the limit is rarely the engine a parkrun measures. It is fuel, the long run and pacing discipline. Treat the prediction as what your fitness is worth after a full marathon block, not on the current one.