# How to Estimate Your Race Performance at New Race Distances

If you've been a 5K to 10K runner for a while, and you feel ready to move up to a 15K, a 10-miler, or even a half-marathon, how should you pace yourself at the new distance?

If you run the first few miles too fast, you may blow up before the end. If you run the first few miles too slow, you may finish comfortably but feel disappointed that you could have run better. You need a conversion table, so that you can convert your finishing time at one distance to a target time at a new distance.

Long-time runner and writer Joe Henderson has come up with exactly what you want. The results of his calculations are in the table.

Find your previous race distance in the left-hand column. Then find your target new race distance in the second column. Next, read the conversion factor in the right-hand column, and multiply your finish time for the previous distance by this factor. The result will be a reason-able target time for the new distance.

Henderson points out "You can't know in advance exactly how any race will end. But knowing what you can expect to run gives you a better idea how to start."

Here's an example. Say you've run 45 minutes for a 10K, and you want to try moving up to a 10-miler. The 10K to 10M factor in the table is 1.68. So your target time for the new distance is:

45 x 1.68 = 75:36.

You can achieve this with an even pace of 7:33 per mile.

Now you know how to begin. If you reach the halfway mark feeling a little stressed, then maybe your training wasn't quite up to the demands of the new distance. You can back off a little and still finish feeling good.

If you reach the halfway point comfortably, you can either continue or pick up your pace a few seconds a mile and find out if this still feels good.

Use Henderson's factors to calculate your starting pace for new distances. Then listen to your body as you pass the mile markers, and make corrections so you can learn how to handle new goals comfortably. After one race at the new distance, you'll have a good idea how to adjust so that you can you can achieve your best at your new goal.

Notice there's no factor in the list to convert a 10K to a marathon...that's 20 miles longer! It's a good idea to run a 20K or 1/2 marathon before tackling the marathon.

("Joe Henderson's Running Commentary," 1990, No. 182, pp. 2-3)

Previous
Distance

Target
Distance

Conversion
Factor

5K

5M/5K

1.66

5K

10K

2.10

5M

10K

1.28

5M

15K

1.97

5M

10M

2.10

10K

15K

1.55

10K

10M

1.68

10K

20K

2.10

15K

10M

1.08

15K

20K

1.37

15K

1/2 Marathon

1.45

15K

25K

1.74

10M

20K

1.27

10M

1/2 Marathon

1.34

10M

25K

1.61

20K

1/2 Marathon

1.06

20K

25K

1.20

1/2 Marathon

Marathon

2.10

25K

Marathon

1.76