How do I predict a marathon from a 10K?

Multiply your 10K by roughly 4.6, which is what Riegel’s formula does for this jump. Then sanity check it against your long-run mileage, because the formula assumes endurance you may still be building.

Is a 10K marathon prediction accurate?

Less so than one from a half marathon. The 10K cannot test the last hour of a marathon, where fueling and muscular fatigue decide your time, so the prediction tends to run optimistic.

Should I trust my predicted marathon pace from a 10K?

Only if your training backs it up. Use it as a target, verify it with long runs at marathon effort, and start race day a few seconds slower than predicted to leave room for the back half.

Predict Your Marathon Time From a 10K

Ran a 10K lately? Enter your time to see what it predicts for the Marathon, plus the pace you would need to hold.

Your 10K time

min

sec

Pace in

Predicted Marathon time

3:27:01

That is 7:54 per mi.

Worked example

A 10K of 45:00 predicts a Marathon of about 3:27:01, a pace of 7:54 per mi. Change the time above to run the same math on your own result.

How a 10K predicts your Marathon

A 10K can predict a marathon, but you are asking it to reach across more than four times the distance, into territory it cannot fully see. The formula turns your 10K speed into a marathon time on the assumption that your endurance scales right along with it, and for most runners that assumption is generous.

A useful way to read the result is that a 10K based marathon prediction is roughly your 10K time multiplied by four and a half to four and two thirds. That is a fine starting goal if your training has the volume to support it. If your long runs and weekly mileage are modest, treat the number as optimistic and build the endurance before you commit to the pace.

The endurance gap between 10K and 42K

A 10K is run almost entirely at or near your aerobic threshold, and it is over in well under an hour. A marathon is run below that threshold but for three, four, or five hours, and the last ten kilometers are governed by fueling, hydration, and muscular fatigue rather than raw fitness. The 10K never visits that part of the race, so the formula has no information about how you will hold up there.

Bridge the gap with long runs and marathon-pace work. If you are averaging good weekly mileage with regular runs of eighteen miles or more, a 10K based marathon time is reachable. Without that base, add ten to twenty minutes to the prediction and let your training prove the rest.

Want every distance at once? The race pace predictor shows your time for the whole range and prints a pace band, and the VDOT calculator turns this race into your training paces.

Related predictions

10K to Marathon questions

How do I predict a marathon from a 10K?: Multiply your 10K by roughly 4.6, which is what Riegel’s formula does for this jump. Then sanity check it against your long-run mileage, because the formula assumes endurance you may still be building.
Is a 10K marathon prediction accurate?: Less so than one from a half marathon. The 10K cannot test the last hour of a marathon, where fueling and muscular fatigue decide your time, so the prediction tends to run optimistic.
Should I trust my predicted marathon pace from a 10K?: Only if your training backs it up. Use it as a target, verify it with long runs at marathon effort, and start race day a few seconds slower than predicted to leave room for the back half.