VDOT Calculator & Race Predictor

Choose a representative race result

Use a recent, hard race or time trial on a reasonably flat course. A result affected by illness, extreme heat, strong wind, altitude, or heavy fatigue describes that day more than your current fitness.

Predictions are strongest near the distance you entered. A fast 5K does not prove marathon readiness, and a marathon result may understate short-distance speed when the athlete has not trained for it.

Use the optional comparison to model two performances independently. The displayed target range uses each score as an endpoint; it never averages the scores or diagnoses why they differ. For example, this model gives 38.3 for a 25:00 5K and 40.0 for a 50:00 10K, producing marathon endpoints of 3:49:34 and 3:57:55.

Read equivalent times as conditional predictions

Equivalent times show performances with similar modeled aerobic demand. They assume suitable training, pacing, fueling, terrain, and weather for the target event. Treat them as comparison points, not promises.

VDOT is also not a laboratory VO2 max result. It combines modeled oxygen demand with how much of that demand a runner can sustain for the duration entered.

Interpret the transparent pace references

The five pace rows are transparent equation-derived references made by applying the displayed oxygen-demand fractions to the calculated score. They are not the official current VDOT lookup-table paces, heart-rate zones, or individualized prescriptions. Faster is not automatically better: use effort, session purpose, and recovery to decide whether a reference fits.

• Update paces from a real current performance, not an aspirational goal time.
• Use effort and recovery to adjust for hills, heat, wind, and surface.
• Recalculate after a race or test that clearly represents new fitness.