Home › Running › Race Time Predictor

Race Time Predictor

Predict your 5K, 10K, half marathon or marathon time from a recent race, using the Riegel formula.

How it's calculated

Peter Riegel's formula, published in 1977 and still the standard: predicted time = known time × (target distance ÷ known distance)^1.06. It assumes you have trained for the longer distance. For marathons, most runners finish a few minutes slower than predicted.

Example

A 25:00 5K predicts a 3:59:47 marathon.

Predictions from common 5K times

5K	10K	Half marathon	Marathon
16:00	33:22	1:13:36	2:33:27
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

Put this calculator on your website: free

Running clubs, coaches, race directors, leagues and team websites: give your members a pace chart or stat calculator right on your own site. Copy the code below and paste it into any page. No sign-up and no cost. It stays up to date automatically.

<iframe src="https://sportsums.com/embed/running/race-time-predictor/" title="Race Time Predictor" width="100%" height="420" style="border:1px solid #ddd;border-radius:10px;max-width:760px" loading="lazy"></iframe>
<p style="font-size:12px;margin:4px 0 0">Race Time Predictor by <a href="https://sportsums.com/running/race-time-predictor/" rel="nofollow">Sport Sums</a></p>

See all calculators you can embed

Race Time Predictor

How it's calculated

Example

Predictions from common 5K times

Put this calculator on your website: free

More running calculators