Half Marathon Time Predictor
The half marathon is where endurance truly starts to matter. At 21.1 kilometers, pacing, nutrition, and aerobic fitness all become critical factors. This predictor analyzes your existing race performances to project a realistic half marathon time — helping you set an honest goal and plan your race strategy.
How it works
Half marathon prediction requires understanding how your body handles sustained aerobic effort. The model combines VDOT estimation (which accounts for oxygen cost at race pace), Riegel scaling from shorter distances, and critical speed analysis from your endurance profile. Because the half marathon stresses different energy systems than a 5K or 10K, the model adjusts for the additional fatigue factors that emerge beyond 15 kilometers.
Training advice
Half marathon training demands a strong aerobic foundation. Your long run should gradually build to 18-21 km, and weekly tempo runs at half marathon goal pace are essential. Practice your race-day nutrition strategy during training — fueling becomes important at this distance. Aim for at least 12-16 weeks of dedicated training, with your peak mileage 3-4 weeks before race day.
Frequently asked questions
Can I predict my half marathon from a 10K time?
Yes — a 10K time is one of the best predictors for half marathon performance. Enter your 10K time and the model will estimate your half marathon potential. Adding a 5K time as well increases accuracy.
What is a good half marathon time?
For recreational runners, finishing under 2 hours is a common goal. Competitive club runners target sub-1:30, and elite runners finish under 1:05. The average half marathon finish time is around 2:00-2:15.
How much slower is half marathon pace than 10K pace?
Typically, half marathon pace is 15-25 seconds per kilometer slower than 10K pace. The exact difference depends on your endurance profile — runners with strong aerobic bases see smaller slowdowns.
Should I run the whole half marathon without walking?
Not necessarily. Many successful half marathon runners use a run-walk strategy, especially in their first race. The key is finishing with a strong effort, regardless of strategy.
Related tools
- Marathon Time Predictor
- 10K Time Predictor
- Half Marathon to Marathon Predictor
- Running Pace Calculator
- Split Calculator