Race Time Predictor
Takes one recent race result and projects finish times for every standard distance from 1500 m to the marathon using the Riegel endurance formula T2 = T1 × (D2/D1)^1.06. The exponent is adjustable: well-trained endurance runners hold their pace better (closer to 1.05), while speed-oriented runners fade more over distance (closer to 1.08).
Read the full guide to this tool
Results
Notes
- The Riegel formula assumes you are equally trained for both distances; predicting a marathon from a 5K usually flatters you unless weekly mileage supports it.
- Predictions work best between distances within a factor of about four of each other.
- Educational estimate for sport and training purposes, not professional coaching or medical advice.
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