Race time predictor.
Every distance, one recent race.

Enter a recent race. Get projected finish times across every common distance using Jack Daniels’ VDOT.

Free tool · Updated April 19, 2026

Get early accessJump to the calculator

Your race times

Recent race distance

Finish time

VDOT 45. Your current fitness, in Jack Daniels’ terms. Every prediction below assumes the same training condition and a flat course.

Predicted finish times

  • 1 mile6:28
  • 10K45:37
  • Half marathon1:41:07
  • Marathon3:30:03

Predictions are the floor, not the ceiling. Reshape builds the weeks that turn them into finish times.

How VDOT prediction works

Daniels treats every race result as a VO2max number. Run a 5K in 22:00 and the model says “this is what VO2max was doing at that moment.” That number is called VDOT. Predicting a marathon from a 5K means asking: at the same VDOT, what finish time matches the 42.195 km distance?

The math accounts for the fact that longer races require a lower sustainable percentage of VO2max. A 5K is run near 100% effort; a marathon closer to 80%. That asymmetry is baked into the percent-of-VO2max curve Daniels derived from race data.

The limit: prediction assumes you’re trained for the target distance. A sharp 5K runner who’s never run over 10 km will underperform the model’s marathon number. Specificity matters.

Common questions

VDOT predictions are accurate to within a few percent for trained runners racing on flat courses. They assume similar training specificity — if you’ve only raced short, a marathon prediction is optimistic until you put the long runs in.

Jack Daniels’ measure of race-specific fitness. Your VDOT is the VO2max value that matches your current race performance. Two runners with the same VDOT should race the same times, regardless of their actual VO2max.

Courses aren’t equal. Weather, hills, elevation, and how specific your training was all matter. Use predictions as a fitness snapshot, not a finish-line promise.

Related calculators

Get early accessBack to home