Free tool
Race time predictor
Enter a recent race to predict your times at other distances and get the training paces that match your fitness.
Your recent race
Finish time
Predicted race times
- 5K
- 23:59
- 7:43 /mi
- 10K
- 50:00
- 8:03 /mi
- Half marathon
- 1:50:19
- 8:25 /mi
- Marathon
- 3:50:01
- 8:46 /mi
Fitness score 40.0 · Riegel exponent 1.06
Training paces from this race
- Easy9:50-10:49 /mi
- Steady8:51-9:19 /mi
- Threshold8:07-8:21 /mi
- Interval7:23-7:42 /mi
Equivalent times
Race equivalency chart
Predicted times from a 5K result using the Riegel formula. Longer predictions assume you've trained for the distance.
| 5K | 10K | Half marathon | Marathon |
|---|---|---|---|
| 18:00 | 37:32 | 1:22:48 | 2:52:38 |
| 20:00 | 41:42 | 1:32:00 | 3:11:49 |
| 22:00 | 45:52 | 1:41:12 | 3:31:00 |
| 24:00 | 50:02 | 1:50:24 | 3:50:11 |
| 26:00 | 54:12 | 1:59:36 | 4:09:22 |
| 28:00 | 58:23 | 2:08:48 | 4:28:33 |
| 30:00 | 1:02:33 | 2:18:00 | 4:47:44 |
| 32:00 | 1:06:43 | 2:27:12 | 5:06:55 |
| 34:00 | 1:10:53 | 2:36:24 | 5:26:06 |
| 36:00 | 1:15:03 | 2:45:36 | 5:45:17 |
| 38:00 | 1:19:14 | 2:54:48 | 6:04:28 |
| 40:00 | 1:23:24 | 3:04:00 | 6:23:39 |
How it works
Two proven formulas
Race times come from Pete Riegel's 1981 formula, T2 = T1 × (D2 ÷ D1)^1.06, still the most widely used way to compare performances across distances.
Training paces come from Daniels-style training paces: Jack Daniels' published formulas convert your race into a fitness score and set easy, threshold and interval paces as shares of it.
PaceLadder uses both to put a target pace on every run in your training plan.
How accurate are race time predictions?
For races of similar length, usually within a few percent. Predictions over a big jump in distance, like 5K to marathon, assume you've done the endurance training for the longer race. Without it, expect to run slower than predicted.
What is the Riegel formula?
Published by Pete Riegel in 1981: T2 = T1 × (D2 ÷ D1)^1.06. It scales a known race time to a new distance, with the 1.06 exponent capturing how pace slows as distance grows.
What is the fitness score?
An estimate of your aerobic capacity, worked out from a race result with the published formulas of Jack Daniels and Jimmy Gilbert. It sets your easy, threshold and interval training paces. PaceLadder is not affiliated with The Run SMART Project.
Which race should I use?
A recent, all-out race on a reasonably flat course. Your most recent result is better than your best one from years ago. A half marathon predicts a marathon better than a 5K does.
- Free toolPace calculatorFind the pace for any finish time, or the time for any pace.
- Free toolRace time predictorTurn a recent race into predicted times and training paces.
Free to start
Start free. Unlock the full plan when it's yours.
Answer a few questions and see your phases, weekly mileage, paces and the first 2 weeks day by day for free. Unlock every session, calendar sync and the PDF when you're ready.
- Your whole plan, day by day. Every week from first run to race day.
- Personal paces in every session. Warm-up, main set and cool-down targets.
- Live calendar sync. Google, Apple and Outlook. Updates when you change your plan.
- Printable PDF. The full plan and workout guide for the fridge.
- Unlimited rebuilds. New race, new goal, new schedule, any time.
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