Race Time Predictor
Enter one recent race result and this tool estimates your finish time at five other distances -- from 5K up to marathon -- along with training paces for easy, marathon, threshold, and interval effort. Estimates come from four independently published formulas (Riegel, Daniels & Gilbert's VDOT, a simple linear extrapolation, and Purdy's world-record-percentage method), so you can compare where they agree.
Enter one recent race result to estimate your times at other distances and your training paces.
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Enter a recent finish time to see predictions.
Ready to put a prediction to the test? Browse full marathons and half marathons across Southeast Asia.
Frequently asked questions
How accurate are race time predictors?
They're a solid starting estimate, not a guarantee. Predictions assume similar training and conditions across distances -- a strong 10K result predicts a marathon less reliably than it predicts a 5K, since endurance and fueling matter more the longer the race gets.
What is VDOT?
VDOT is Jack Daniels' measure of running fitness, derived from a recent race result's pace and duration. It's used to predict equivalent performances at other distances and to set training paces for easy, marathon, threshold, and interval runs.
Can I predict a marathon time from a 10K result?
Yes, though accuracy drops the bigger the gap between the reference and target distance. A recent half marathon predicts a marathon more reliably than a 10K does, since it better reflects your endurance at marathon-relevant durations.
Which prediction method should I trust -- Riegel, Daniels, linear, or Purdy?
None is definitively "best" -- they’re four different published models, and where they agree is generally more trustworthy than where they diverge. Riegel and Daniels are the two most widely used for age-group runners.