Race Predictor
Predict your finish time for a marathon or 10K based on a previous race result.
Previous Race Data
Target Race
Note: This uses the Riegel Formula (a factor of 1.06). It assumes consistent training and race conditions. Actual results may vary due to terrain and weather.
How does the Race Predictor work?
This calculator uses the **Riegel Formula**, developed by Peter Riegel, which is considered the standard for race time prediction.
The formula states that the pace at distance D1 is related to the pace at distance D2 by the relationship:
T2 = T1 × (D2 / D1)1.06
- T1: Your previous race time
- T2: Predicted time for new distance
- D1: Distance of previous race
- D2: Distance of target race
- 1.06: The standard fatigue factor (exponent)
Factors Affecting Race Performance
While the Riegel formula is accurate for well-trained runners, it does not account for:
- Terrain: Hills, trails, or flat roads significantly impact pace.
- Weather: Heat, humidity, and wind resistance.
- Specificity: Sprinters may not hold pace in a marathon as well as endurance runners.