Guide / Running
Race time equivalents
Every whole-minute 5K time from 15:00 to 40:00, converted to a predicted mile, 10K, half marathon and marathon. A second table gives the pace each prediction implies.
How the equivalents are worked out
The chart uses the same formula as the race time predictor: T2 = T1 × (D2 ÷ D1)1.06. Here D1 and T1 are the race you ran, and D2 is the distance you want a time for, which comes out as T2. It is usually called Riegel's formula.
Starting from a 5K, the distance ratios are fixed, so each column is the 5K time times a constant. The mile is 0.3007 of the 5K time, the 10K 2.0849 times it, the half 4.6002 times and the marathon 9.5911 times.
The power of 1.06 is what builds in slowing down. Twice the distance takes a bit more than twice the time. Over the 8.4-fold jump from 5K to marathon, that bit adds up to roughly 14% more time than pace alone would suggest.
5K time to predicted race times
Every 5 minutes| 5K | 1 mile | 10K | Half | Marathon |
|---|---|---|---|---|
| 15:00 | 4:31 | 31:16 | 1:09:00 | 2:23:52 |
| 16:00 | 4:49 | 33:22 | 1:13:36 | 2:33:27 |
| 17:00 | 5:07 | 35:27 | 1:18:12 | 2:43:03 |
| 18:00 | 5:25 | 37:32 | 1:22:48 | 2:52:38 |
| 19:00 | 5:43 | 39:37 | 1:27:24 | 3:02:14 |
| 20:00 | 6:01 | 41:42 | 1:32:00 | 3:11:49 |
| 21:00 | 6:19 | 43:47 | 1:36:36 | 3:21:25 |
| 22:00 | 6:37 | 45:52 | 1:41:12 | 3:31:00 |
| 23:00 | 6:55 | 47:57 | 1:45:48 | 3:40:36 |
| 24:00 | 7:13 | 50:02 | 1:50:24 | 3:50:11 |
| 25:00 | 7:31 | 52:07 | 1:55:00 | 3:59:47 |
| 26:00 | 7:49 | 54:12 | 1:59:36 | 4:09:22 |
| 27:00 | 8:07 | 56:18 | 2:04:12 | 4:18:58 |
| 28:00 | 8:25 | 58:23 | 2:08:48 | 4:28:33 |
| 29:00 | 8:43 | 1:00:28 | 2:13:24 | 4:38:09 |
| 30:00 | 9:01 | 1:02:33 | 2:18:00 | 4:47:44 |
| 31:00 | 9:19 | 1:04:38 | 2:22:36 | 4:57:19 |
| 32:00 | 9:37 | 1:06:43 | 2:27:12 | 5:06:55 |
| 33:00 | 9:55 | 1:08:48 | 2:31:48 | 5:16:30 |
| 34:00 | 10:13 | 1:10:53 | 2:36:24 | 5:26:06 |
| 35:00 | 10:31 | 1:12:58 | 2:41:00 | 5:35:41 |
| 36:00 | 10:50 | 1:15:03 | 2:45:36 | 5:45:17 |
| 37:00 | 11:08 | 1:17:09 | 2:50:12 | 5:54:52 |
| 38:00 | 11:26 | 1:19:14 | 2:54:48 | 6:04:28 |
| 39:00 | 11:44 | 1:21:19 | 2:59:24 | 6:14:03 |
| 40:00 | 12:02 | 1:23:24 | 3:04:00 | 6:23:39 |
Same code as the race time predictor with 5K as the race entered. Distances: 1 mile = 1.609344 km, half = 21.0975 km, marathon = 42.195 km. Computed at full precision, with each displayed time rounded to the closest second (halves round up).
Pace for each prediction (/km · /mi)
Every 5 minutes| 5K | 5K pace | 10K pace | Half pace | Marathon pace |
|---|---|---|---|---|
| 15:00 | 3:00 · 4:50 | 3:08 · 5:02 | 3:16 · 5:16 | 3:25 · 5:29 |
| 16:00 | 3:12 · 5:09 | 3:20 · 5:22 | 3:29 · 5:37 | 3:38 · 5:51 |
| 17:00 | 3:24 · 5:28 | 3:33 · 5:42 | 3:42 · 5:58 | 3:52 · 6:13 |
| 18:00 | 3:36 · 5:48 | 3:45 · 6:02 | 3:55 · 6:19 | 4:05 · 6:35 |
| 19:00 | 3:48 · 6:07 | 3:58 · 6:23 | 4:09 · 6:40 | 4:19 · 6:57 |
| 20:00 | 4:00 · 6:26 | 4:10 · 6:43 | 4:22 · 7:01 | 4:33 · 7:19 |
| 21:00 | 4:12 · 6:46 | 4:23 · 7:03 | 4:35 · 7:22 | 4:46 · 7:41 |
| 22:00 | 4:24 · 7:05 | 4:35 · 7:23 | 4:48 · 7:43 | 5:00 · 8:03 |
| 23:00 | 4:36 · 7:24 | 4:48 · 7:43 | 5:01 · 8:04 | 5:14 · 8:25 |
| 24:00 | 4:48 · 7:43 | 5:00 · 8:03 | 5:14 · 8:25 | 5:27 · 8:47 |
| 25:00 | 5:00 · 8:03 | 5:13 · 8:23 | 5:27 · 8:46 | 5:41 · 9:09 |
| 26:00 | 5:12 · 8:22 | 5:25 · 8:43 | 5:40 · 9:07 | 5:55 · 9:31 |
| 27:00 | 5:24 · 8:41 | 5:38 · 9:04 | 5:53 · 9:28 | 6:08 · 9:53 |
| 28:00 | 5:36 · 9:01 | 5:50 · 9:24 | 6:06 · 9:50 | 6:22 · 10:15 |
| 29:00 | 5:48 · 9:20 | 6:03 · 9:44 | 6:19 · 10:11 | 6:36 · 10:37 |
| 30:00 | 6:00 · 9:39 | 6:15 · 10:04 | 6:32 · 10:32 | 6:49 · 10:58 |
| 31:00 | 6:12 · 9:59 | 6:28 · 10:24 | 6:46 · 10:53 | 7:03 · 11:20 |
| 32:00 | 6:24 · 10:18 | 6:40 · 10:44 | 6:59 · 11:14 | 7:16 · 11:42 |
| 33:00 | 6:36 · 10:37 | 6:53 · 11:04 | 7:12 · 11:35 | 7:30 · 12:04 |
| 34:00 | 6:48 · 10:57 | 7:05 · 11:24 | 7:25 · 11:56 | 7:44 · 12:26 |
| 35:00 | 7:00 · 11:16 | 7:18 · 11:45 | 7:38 · 12:17 | 7:57 · 12:48 |
| 36:00 | 7:12 · 11:35 | 7:30 · 12:05 | 7:51 · 12:38 | 8:11 · 13:10 |
| 37:00 | 7:24 · 11:55 | 7:43 · 12:25 | 8:04 · 12:59 | 8:25 · 13:32 |
| 38:00 | 7:36 · 12:14 | 7:55 · 12:45 | 8:17 · 13:20 | 8:38 · 13:54 |
| 39:00 | 7:48 · 12:33 | 8:08 · 13:05 | 8:30 · 13:41 | 8:52 · 14:16 |
| 40:00 | 8:00 · 12:52 | 8:20 · 13:25 | 8:43 · 14:02 | 9:06 · 14:38 |
Pace = predicted time ÷ distance, per kilometer then per mile, each rounded to the nearest second, as the predictor shows them. Mile pace for the 1-mile prediction is the mile time itself, so it is left out.
Reading the chart
Find your most recent 5K in the left column. Read across for what the formula says you could run at the other distances. The pace table shows what you would need to hold to get there.
Take a 25:00 5K. The chart predicts 52:07 for 10K, 1:55:00 for a half marathon and 3:59:47 for a marathon. The paces climb from 5:00/km for the 5K to 5:41/km for the marathon. That spread of 41 seconds per km is the formula's picture of how much a runner slows over the longer race.
If your 5K falls between two whole minutes, the predictor takes it to the second. Between rows, each extra minute on the 5K adds about 2:05 to the 10K, 4:36 to the half and 9:35 to the marathon.
When the formula holds
The formula describes a typical trained runner. It works best under a few conditions, all of which the predictor's own page sets out.
- The two races are fairly close in distance. A 5K predicts a 10K far better than it predicts a marathon. The further apart the distances, the more the result is extrapolation.
- Your training covers the longer race. The formula assumes the endurance is already there. It has no way to check.
- Each race takes somewhere from 3.5 minutes to 4 hours. The predictor gives that window as the one the formula was framed for.
- The two races are run in similar conditions. Similar course, similar weather, similar effort.
The four-hour limit cuts into this chart. Any 5K slower than about 25:01 predicts a marathon over four hours. From that row down, the marathon column is outside the range the formula was meant for, so read it with extra caution.
When it doesn't
The most common miss is the marathon. Plenty of people run a sharp 5K on modest weekly mileage. That fitness carries over to 10K well, and to a half reasonably. It rarely carries the full way to a marathon without long runs behind it.
Runners also differ in shape. Some hold pace well as races get longer and beat the prediction at long distances. Others are quicker over short races and fall short of it. One exponent can't tell which kind you are. Your own results at two distances can.
Conditions matter too. A fast, flat 5K on a cool morning will predict a marathon that a hilly, hot race day won't allow.
A practical way to use the chart is as a check rather than a target. If your 10K comes in well slower than your 5K predicts, longer aerobic work is the likely gap. If it comes in faster, your endurance is ahead of your speed.
Every time on this page is a formula output. It is general information, and neither a training plan nor medical advice. A predicted time is not evidence you are ready for that distance. Build up to a new distance gradually. Where heart or lung problems are involved, or an injury is still healing, get medical advice first.
Common questions
What do I multiply a 5K time by to get a 10K time?
Multiply the 5K time by about 2.0849. That is 2 raised to the power 1.06, because a 10K is twice the distance. A 20:00 5K predicts 41:42, and a 25:00 5K predicts 52:07. The chart has every whole minute from 15:00 to 40:00.
What 5K time predicts a sub-50 10K?
About 23:58 or faster. A 23:58 5K predicts 49:58 for 10K. At 23:59 the prediction rounds to exactly 50:00, and a 24:00 5K predicts 50:02.
How do I convert a 10K time to a half marathon?
Multiply by about 2.2064, which is the half's distance ratio of 2.10975 raised to the power 1.06. A 45:00 10K predicts 1:39:17, a 50:00 10K predicts 1:50:19, and a 55:00 10K predicts 2:01:21. Select 10K as the race entered in the predictor for any other time.
How much marathon time is one minute of 5K worth?
About 9 minutes 35 seconds. The marathon multiplier from a 5K is 9.5911, so every minute taken off a 5K takes that much off the predicted marathon. The same minute is worth about 2:05 at 10K and 4:36 at the half.