A free web calculator that estimates VO2 max using three field-test methods: the Cooper 12-minute run, the Rockport 1-mile walk, and a heart-rate-ratio method so you don't need a lab test or a wearable to get a reasonable estimate. Results are benchmarked against peer-reviewed FRIEND registry percentile data, so you can see where your number sits for your age and sex, not just a raw figure. Supports metric and imperial units.