- 1Enter your Recent Race Distance (km) and actual completion time (Hours, Minutes, Seconds).
- 2Select your Target Event distance (5k, 10k, Half Marathon 21.1k, or Marathon 42.2k).
- 3View your predicted finish time estimated using the Riegel fatigue model.
The Race Time Predictor estimates performance for longer or shorter distances based on a recent race result. It utilizes Peter Riegel’s endurance formula, which incorporates a fatigue factor exponent.
Where T1 is recent time, D1 is recent distance, D2 is target distance, and 1.06 is the standard fatigue exponent.
T₂ = T₁ × (D₂ / D₁)¹.⁰⁶Scales a recent finish time to a new distance using a fatigue exponent of 1.06.
Predicted Time = Recent Time × (Target Distance ÷ Recent Distance) ^ 1.06T₂ = 1,470 sec × (10 / 5)¹.⁰⁶ = 1,470 × 2.085 = 3,065 secT2 = T1 × (D2/D1)^1.06 = 1500 s × (10/5)^1.06 ≈ 1500 × 2.0849 ≈ 3127 sT2 = 3000 s × (21.0975/10)^1.06 ≈ 3000 × 2.2064 ≈ 6619 s- Assumes Equal Aerobic Training: The Riegel formula assumes you have completed appropriate endurance training for the longer target distance.
- Fatigue Exponent (1.06): Represents an average runner. If stepping up from 5k to a full Marathon without long runs, actual times may be slower.
- The prediction assumes the recent race was an honest all-out effort at a distance not too far from the target.
What is the Riegel formula?
The Riegel formula (T2 = T1 * (D2/D1)^1.06) is a standard mathematical model developed by Peter Riegel to predict race performance across different distances.
Is a race prediction guaranteed?
No. Race predictions are estimates that assume proper distance-specific training, favorable weather, and effective pacing.
What model does the prediction use?
Peter Riegel's endurance formula: predicted time = recent time × (target distance / recent distance) raised to the power 1.06. The exponent reflects that pace slows slightly as distance grows.
How accurate is the prediction?
It is a mathematical estimate that assumes similar course, conditions, and training. It works best for races reasonably close in distance to your recent result.