Race Time Predictor

Enter a recent race result. We’ll predict your times at every other common distance using either the Riegel formula or Jack Daniels’ VDOT.

Format: mm:ss or h:mm:ss.

Predictions assume even pacing and that you’re equally well-trained for every distance. Real race day depends on pacing, heat, hills, and how specific your training was. Use as a guide, not a guarantee.

How this is calculated

Riegel uses the empirical formula T2 = T1 × (D2 / D1)1.06. It’s simple and reasonably accurate for distances close to your input. Tends to be slightly optimistic for the marathon.

VDOT (Jack Daniels) is a fitness score based on the oxygen cost of running velocity and the fraction of VO2max sustainable at race duration. It models how much speed you can hold for longer durations, and is generally more conservative across big distance jumps.