How to Predict Running Race Times

Tattooed female marathon runner checking smart watch in urban park
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Predicting a race time, especially for a long-distance race like a marathon, is tough because there are so many variables, such as physical and mental preparation for the race, weather, elevation on the course, crowds, etc.

Use a Table

However, if you've recently run another race at a different distance, one way to give yourself a rough estimate of what you're capable of running is to use a chart such as the one below.

Look for your most recent race time in one of the columns on the left, then follow it across to your predicted marathon finish time.

1-mile    5-K          10-K      Half-marathon   Marathon

4:20       15:00        31:08          1:08:40              2:23:47

4:38       16:00        33:12          1:13:19              2:33:25

4:56       17:00        35:17          1:17:58              2:43:01

5:14       18:00        37:21          1:22:38              2:52:34

5:33       19:00        39:26          1:27:19              3:02:06

5:51       20:00        41:31          1:31:59              3:11:35

6:09       21:00        43:36          1:36:36              3:21:00

6:28       22:00       45:41           1:41:18              3:30:23

6:46       23:00       47:46          1:45:57               3:39:42

7:05       24:00       49:51           1:50:34              3:48:57

7:24       25:00       51:56           1:55:11              3:58:08

7:42       26:00       54:00          1:59:46              4:07:16

8:01      27:00        56:04          2:04:20              4:16:19

8:19      28:00        58:08          2:08:53              4:25:19

8:37      29:00        1:00:12       2:13:24              4:34:14

8:56      30:00        1:02:15       2:17:53              4:43:06

Use a Calculator

To get a more exact prediction, you can also use a race time predictor calculator, such as this race time predictor calculator. You just plug in your data. The calculator then shows you how you might perform in races at other distances.

You need to also keep in mind that the race time predictions are estimates of the time you might achieve if you do the appropriate training for that distance. So it doesn't mean that if you train for a 5K and achieve a good time, then you'll automatically run the corresponding marathon time. In addition, as I said, there are so many variables that could affect your time. For example, no two courses are exactly alike and running a hilly vs. flat course or high altitude vs. sea level will definitely slow you down.

You're more likely to get an accurate prediction for a marathon based on a half-marathon time, rather than a 5K. It's also good to use a time from a race no more than six weeks before your race. If it's more time than that, your fitness level may have changed (for better or worse) and the times won't be as accurate. Also, if you're running local races, running a race within a few weeks of your target race increases your chances of having similar weather conditions for both races, which will also make your time prediction more realistic.

There's obviously a large margin of error when using race predictor calculators, but it's helpful to have a rough estimate before a race, rather than going into it blindly. It can definitely keep you from setting race goals and prevent pacing mistakes, such as going out too fast.

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Article Sources
  • “Oxygen Power: Performance Tables for Distance Runners,” by Jack Daniels and J.R. Gilbert.