Race Time Predictor
Predict your finish time at another distance using Riegel's formula.
Known time (h:m:s)
Predicted finish time
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Predict your finish time at a different race distance using Riegel's formula — enter a known time at one distance (5K to marathon) to estimate your time at another.
Frequently asked questions
What formula does this use?
Riegel's formula (Peter Riegel, 1977): T2 = T1 × (D2 / D1)^1.06 — a widely used model that accounts for the fact that pace naturally slows over longer distances due to fatigue.
How accurate is the prediction?
It's a solid estimate for well-trained runners at similar distances, but gets less precise the bigger the gap between your known distance and the target (e.g. predicting a marathon from a 5K is less reliable than from a half marathon).