Half Marathon Time Predictor
Predict your 21.1 km half marathon finish time from 5K or 10K race results
Input Parameters
Real-time calculation updates dynamically as you adjust inputs. Values remain strictly local on your device.
Predicted Half Marathon Time5:01 min/km
1:45:54HH:MM:SS
Target pace: 5:01 per km (8.07 min/mile)
Speed
11.95km/h
Expected 10K Split
48:00HH:MM:SS
Clinical Responsibility Note: This calculation provides statistical estimations for informational and educational purposes only. It is not an individualized medical diagnosis or clinical prescription.
Mathematical Formula & Scientific Methodology
Formula: Riegel Half Marathon Projection
T(21.1K) = T1 × (21.0975 / D1)^1.06Models endurance fatigue degradation over the 21.0975 kilometer distance.
Model Assumptions
- Long runs of at least 15-18 km in training
- Proper fueling and hydration
Variables & Standard Units
| Symbol | Physiological Meaning | Unit |
|---|---|---|
| T1 | Recent 5K or 10K finish time in seconds | seconds |
| D1 | Distance of benchmark race | km |
Scientific Limitations
- If long runs have not exceeded 12 km, actual finish time may degrade beyond predicted time due to glycogen depletion
Frequently Asked Questions
Related Calculators & Next Steps
Running & Pace
Half Marathon Pace Calculator
Calculate target pace and 5K interval splits for 21.0975 km half marathons
Calculate now
Running & Pace
Marathon Time Predictor
Predict your 42.195 km marathon finish time from half marathon or 10K times
Calculate now
Running & Pace
10K Time Predictor
Predict your 10,000m race finish time from 5K, half marathon, or marathon times
Calculate now