VO2max calculator — no lab, no max test

0:03 · Why we built it

Every watch and every calculator gives you your VO2max — and most of them stop at the number. We wanted the other half: how far off that number can be for you, and where the sum came from. So we built one that shows its range, names its source, and says out loud where it bends.

0:25 · Who it is for

It is for runners and cyclists who want a rough idea of their engine without booking a lab. It is also for anyone curious whether a winter of training has moved the number.

0:40 · How it works: heart rates only

The simplest route asks for two heart rates: your resting rate — forty-eight here — and your true maximum, one eighty-eight. The answer appears as you type: sixty millilitres per kilogram per minute. The sum behind it is short: fifteen point three times your maximum, divided by your resting rate. If you have no maximum on record, leave that field empty; the tool estimates one from your age and widens the range to match.

1:12 · Routes 2 and 3: power meter, or a steady pace

If you own a power meter, the second route wants one steady ride of at least six minutes. Type the power, the heart rate it settled at, your age and your weight — here one thirty watts at one forty-two. Without a power meter, a flat course and a steady pace do the same job on the third route. It is the roughest of the three, and the tool says so.

1:40 · What comes out, and how to read it

Every answer comes as a whole number with a range under it — here, somewhere between fifty-five and sixty-five. That range held ninety-five percent of the men in the study, and the range is the part to read. With a band that wide, a decimal would promise a precision the method does not have. For the first two routes that range comes from the studies themselves. For the running route it is our own estimate — the page says so. Under each result sits "Where it bends": who the sum was measured on, and for whom it holds less well. For this route, that was forty-six well-trained men; if that is not you, read it as a rough indication.

2:30 · What you need

For the heart-rate route: a chest strap, and your resting rate lying down, first thing after waking. And your maximum — the highest your strap has recorded in a real all-out effort. Take that resting rate over a few mornings: five beats too high moves the answer by about ten percent. For the bike route: a power meter and a chest strap, six steady minutes at one power, heart rate from the last minute. For the running route: a flat course, a chest strap, six steady minutes at one pace — a run, three to seven-thirty per kilometre.

3:11 · Where to find it

The calculator is free, at enduranceproof dot com slash tools. What the number means once you have it — and what it doesn't — is in our explainer on the same site.