Predict
Half marathon time predictor
Your recent race
MetricSplit ladder
Equivalent efforts- 10K44:304:27 /km
Your entered race is marked; every other row is projected from it.
Worked example
A 44:30 10K projects to a 1:38:11 half marathon at 4:39/km — twelve seconds per kilometre slower than 10K pace, which is the endurance cost of doubling the distance.
Common questions
- How accurate is a half marathon prediction from a 10K?
- The 10K to half step is one of the more reliable projections, because the two races sit close together on the endurance curve. Expect it within two to three minutes for a trained runner.
- Should I use a 5K or a 10K as my input?
- Whichever you raced most recently and hardest. The 10K is closer to half-marathon effort, so it generally projects better than a 5K.
- Why is my predicted pace slower than my 10K pace?
- Sustainable pace falls as distance rises. The half is roughly twice the 10K, and Riegel's 1.06 exponent turns that into about twelve seconds per kilometre.