Race Time Predictor
Predict your finish time for any race distance using the scientifically-validated Riegel formula.
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How It Works
Enter a recent race distance and time. The calculator uses the Riegel formula to predict equivalent times for other distances, accounting for the natural pace slowdown at longer distances.
Tips for Better Results
- •Predictions are most accurate when the input race is similar in distance to your target
- •Marathon predictions from 5K times tend to be optimistic without marathon-specific training
- •Use predictions as targets, not guarantees. Race day conditions matter.
Frequently Asked Questions
Race Predictor
Race predictions using the Riegel formula are typically accurate within 2-5% for well-trained runners. Factors like terrain, weather, and training specificity can affect actual results.
The Riegel formula (T2 = T1 × (D2/D1)^1.06) predicts race times by accounting for the fact that pace naturally slows as distance increases. It was developed by researcher Peter Riegel.
Yes, use a race from the past 4-8 weeks for most accurate predictions. Your fitness changes over time, so older results may not reflect current ability.
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