Race time prediction uses a recent performance to forecast what you could run over a different distance. The most common method is Riegel's formula, which scales your time by the ratio of distances raised to a fatigue exponent (about 1.06). Predictions are most accurate when you've trained specifically for the target distance — a 5K time tends to over-predict marathon ability unless you've built the endurance base.
Key points
- Riegel's formula is the common method
- Most accurate for trained distances
- Longer predictions assume endurance training
- Useful for setting realistic race goals
Try the tool
Put this into practice with our free calculator.
Open the Running Race Time Predictor →