A finish-time predictor turns one recent result into realistic targets for other distances — invaluable for setting race goals and pacing strategy.
How prediction works
The Riegel model recognises that you can't hold your 5K pace for a marathon. Its 1.06 exponent scales your time up as distance grows, capturing the natural slowdown over longer efforts.
Making the prediction real
The formula tells you what's possible given your current speed — but only training the specific distance makes it achievable. Use the prediction to set goal pace, then build the endurance to sustain it.
Frequently asked questions
The Riegel formula is quite accurate when your target distance is within about 3× your input race and you've trained appropriately. Predictions for much longer races assume you've built the specific endurance.
It predicts finish time as T2 = T1 × (D2 ÷ D1)^1.06, where T1 and D1 are a known time and distance. The 1.06 exponent reflects how pace naturally slows over longer distances.
Predictions from a short race assume marathon-specific training. Without the long runs and endurance base, most runners finish slower than a 5K- or 10K-based prediction suggests.