Running calculators › Race time predictor
Race time predictor
Enter one recent race and see what it predicts for a mile, 5K, 10K, half marathon and marathon, by two well-known formulas side by side.
| Distance | Riegel | Daniels (VDOT 33.5) | Pace /km | Pace /mi |
|---|---|---|---|---|
| 1 mile | 8:25 | 8:20 | 5:12 | 8:23 |
| 5K | 28:00 | 28:00 | 5:36 | 9:01 |
| 10K | 58:23 | 58:11 | 5:50 | 9:23 |
| Half marathon | 2:08:48 | 2:08:57 | 6:07 | 9:50 |
| Marathon | 4:28:33 | 4:25:28 | 6:20 | 10:11 |
Paces are the average of the two predictions.
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Race time chart from your 5K
Predicted times from common 5K results, averaging Riegel and Daniels. Assumes you train for the longer distance.
| 5K | 10K | Half marathon | Marathon |
|---|---|---|---|
| 18:00 | 37:26 | 1:22:41 | 2:52:32 |
| 20:00 | 41:35 | 1:31:55 | 3:11:33 |
| 22:00 | 45:45 | 1:41:10 | 3:30:31 |
| 24:00 | 49:55 | 1:50:25 | 3:49:25 |
| 25:00 | 52:00 | 1:55:02 | 3:58:51 |
| 26:00 | 54:06 | 1:59:39 | 4:08:15 |
| 28:00 | 58:17 | 2:08:53 | 4:27:01 |
| 30:00 | 1:02:28 | 2:18:05 | 4:45:42 |
| 32:00 | 1:06:39 | 2:27:16 | 5:04:18 |
| 35:00 | 1:12:56 | 2:41:00 | 5:32:06 |
| 38:00 | 1:19:12 | 2:54:39 | 5:59:44 |
| 40:00 | 1:23:23 | 3:03:44 | 6:18:06 |
| 45:00 | 1:33:49 | 3:26:18 | 7:03:46 |
Questions
How accurate is a race time predictor?
For distances close to the one you raced, usually within a few minutes. The further you predict (a 5K to a marathon), the less certain it gets, because the longer race tests endurance you may not have trained yet. Treat the marathon number as what your speed allows if your training matches.
What is Riegel’s formula?
Peter Riegel’s 1977 rule: time₂ = time₁ × (distance₂ ÷ distance₁)^1.06. It says you slow down a little as races get longer, by about the same proportion each time.
What is VDOT?
Jack Daniels’ fitness score from a race result, based on the oxygen cost of your pace and how long you held it. Two runners with the same VDOT should run similar times at every distance.
Why do the two formulas give different times?
They model fatigue differently. Riegel is often a bit optimistic for the marathon; Daniels tends to be closer for well-trained runners. The truth for most people is somewhere between, which is why the paces use the average.
Which race should I enter?
A recent race or an all-out time trial on a flat course. A 5K or 10K from the last six weeks works best. Don’t use an easy run: the formulas assume you ran as hard as you could.
For goal paces and splits, use the pace calculator or a pace chart. To see the fitness a time needs, try the VO2 max calculator.
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