What VO2 max tells you
VO2 max is the most oxygen your body can use during hard exercise, measured in millilitres per kilogram of body weight per minute. It's one of the best single markers of aerobic fitness. Higher numbers usually mean a stronger heart and lungs, and research links high values to longer life.
A lab test with a mask and a treadmill is the gold standard. It's expensive and exhausting. This estimator uses field tests you can do yourself.
Three ways to estimate
The Uth-Sorensen method uses your resting and maximum heart rate. It's the easiest because you don't have to exercise. It's also the roughest, since it relies on a heart rate maximum you may only be guessing.
The 1.5-mile run test asks you to cover 1.5 miles as fast as you can and enter your time. Fast time, high fitness. Warm up first and run on a flat, even surface.
The YMCA step test has you step up and down on a box for three minutes, then measure your recovery heart rate. It suits people who can't run.
Reading the result
Your score gets a label from Poor to Superior, based on your age and sex. VO2 max falls with age, so a number that's just average at 25 can be excellent at 60. The comparison keeps that in mind, so you're being judged against people like you.
Field estimates have a margin of error. Think of it as plus or minus a few points. They're good for tracking your own progress, less good for comparing yourself to a friend.
Raising it
Train regularly at an easy pace, and add some hard intervals. A classic set is four minutes hard, three minutes easy, repeated four times, once or twice a week. Most of your running should stay comfortable. Genetics set a ceiling, yet most people can improve a good deal when they start from a low base.
Body weight matters because the number is per kilogram. Losing excess weight can lift VO2 max without any change in your engine.
How often to retest
Every six to twelve weeks is enough. Test under the same conditions: same route or box, same time of day, well rested. Otherwise you're measuring your mood, not your fitness.
Check with a doctor before hard testing if you have heart concerns or haven't exercised in a long time. Your numbers stay in your browser.