VO2 Max Calculator (VDOT) from Your Race Time

VO2 max is the most oxygen your body can use in a minute, measured in millilitres per kilogram of body weight (ml/kg/min). A lab measures it with a mask on a treadmill. A race gives you a cheaper route in, because running at a given speed costs a known amount of oxygen, and how long you held that speed tells you what share of your maximum you were using.

That is the logic of Jack Daniels' VDOT, first set out with Jimmy Gilbert in the 1979 performance tables Oxygen Power and developed in Daniels' Running Formula. The calculator turns your average speed into an oxygen cost, estimates the fraction of VO2 max you could sustain for the time you ran, and divides one by the other. Run a 5K in 25:00 and the answer is a VO2 max of 38.3.

Strictly, the number is a VDOT: an effective VO2 max. It is the VO2 max that would explain your race, and it quietly includes your running economy, which is why it can sit above or below a lab result. That makes it less pure than a lab figure and more useful to a runner, because it is the number that predicts what you can run next and sets your training paces.

The table runs the calculator for common results. Find the row closest to your own time, or enter it above for an exact figure.

The same VO2 max produces a different time at every distance. A runner at 38.3 is worth 25:00 for 5K and 51:54 for 10K, and the marathon figure of 3:57:58 assumes marathon training behind it. The shorter the race you enter, the less endurance it tests, so a fast 5K from someone who has never run beyond 10 km will flatter their marathon equivalent.

A race result is only as good as the race. The estimate holds best for a recent, evenly paced, all-out effort on a fairly flat course in cool weather, at any distance from the mile to the marathon. Heat, hills, a fast start that fades, or a marathon run without the long runs behind it all make you look less fit than you are. A downhill course or a tailwind can do the opposite.

A running watch works differently. It never measures oxygen: it infers VO2 max from how your heart rate relates to your pace, which is why a hot day, a poor night's sleep or a loose strap can move the number without any change in fitness. The guide to what VO2 max really measures explains why a watch, a lab and a race can give three different figures for the same runner.

Expect a race-based figure and a watch figure to differ by a few points. When they disagree by more, trust the race if the conditions were good, and the watch if you have not raced for a year. Neither replaces a lab test if you need a clinical number.

Turn it into paces. The training paces calculator uses the same VDOT to set your easy, marathon, threshold, interval and repetition paces, and the speed at VO2 max above is the pace behind the interval sessions.

Put it in context. Our running times by age and gender tables show how a 5K, 10K, half marathon or marathon time compares at your age, and the guide to a good VO2 max for runners has the VO2 max charts by age and sex.

Train around it. Most of your running should sit well below the speed at VO2 max, at an easy aerobic effort: the zone 2 heart rate calculator gives you the heart rate range for those days, and the running plan generator builds the weeks around your goal race. Retest with a fresh race after a training block rather than every week.