Half
Half marathon predictor
Estimate your half marathon (21.1 km) from 5K/10K, zone 2 and weekly km. Built for “what will you run for the half?” content.
- High sensitivity to weekly volume
- Distance experience adjustment
- Block race splits
- 5K / 10K / marathon equivalents
Enter your marks and calculate to see estimated time, pace, splits and equivalents.
How we estimate your half
Half marathons punish low volume and inexperience. The model adds extra fade when weekly km is low or you are new to 21.1K, on top of classic pace extrapolation.
Indicative estimate based on pace and fatigue models. It does not replace a plan with real history, recent tests, or race-day conditions (heat, elevation, HYROX penalties).
I want the predictor with my real history
Create a free account · Pro uses your athlete memory