Predict Your Half marathon Time From a 10K
Ran a 10K lately? Enter your time to see what it predicts for the Half marathon, plus the pace you would need to hold.
Worked example
A 10K of 45:00 predicts a Half marathon of about 1:39:17, a pace of 7:34 per mi. Change the time above to run the same math on your own result.
How a 10K predicts your Half marathon
If you want one race to predict your half marathon, a recent 10K is hard to beat. The two distances share almost the same physiology, both run close to your aerobic threshold for an extended stretch, so the formula has very little guesswork to do. A 10K based half prediction is one of the most trustworthy numbers on this site.
The jump is just over twice the distance, which Riegel handles comfortably. As long as your training includes runs longer than your 10K, the predicted half is a realistic goal rather than a stretch. This is the prediction I lean on most when setting a half marathon target.
Why the 10K is the half marathon’s best predictor
The half marathon lives at the edge of your aerobic threshold, the fastest pace you can hold without lactate piling up. So does a well-run 10K, just for a shorter time. Because both races test the same system, your 10K result is a clean readout of the exact fitness the half demands, which is why the prediction holds up so well.
The only adjustment worth making is for endurance. The half takes most runners ninety minutes to a bit over two hours, so you need long runs to support it. If your weekly long run already reaches ten or eleven miles, trust the prediction. If it tops out at six, the number is still your speed ceiling, you just need a few more weeks of distance to reach it.
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 Half marathon questions
- Is a 10K a good predictor of half marathon time?
- It is one of the best. The two races share nearly the same aerobic-threshold demands, so a recent 10K predicts your half within a couple of minutes for most trained runners.
- How do I convert my 10K to a half marathon time?
- Multiply your 10K by about 2.2. Riegel raises the distance ratio to the power 1.06, which lands close to that for this jump, building in a realistic pace drop over the longer race.
- What do I need to hit the predicted half?
- Mostly endurance. Your 10K proves you have the right pace. Make sure your long runs reach ten miles or more so you can hold that effort for the full distance.