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Maximum heart rate and the five training zones, using the Karvonen method when a resting rate is given.
Max HR = 220 − age · Karvonen: target = HRR·%I + resting
A mind behind this: Martti Karvonen 1918–2009
Leave resting HR at 0 to use the simple % of max; enter it to use Karvonen.
They are five bands of exercise intensity, each defined as a percentage range of your maximum heart rate. Lower zones feel easy and build endurance; higher zones are hard and build speed and power. Training in the right zone for your goal makes exercise more effective than just going as hard as possible every time.
The simplest estimate is 220 minus your age — so a 40-year-old has an estimated max of about 180 beats per minute. It is only an average; real maximums vary by 10 to 20 beats between people of the same age, and the only exact way to know yours is a supervised maximal test.
Karvonen makes the zones more personal by using your heart-rate reserve — the gap between your maximum and your resting heart rate. Each zone percentage is applied to that reserve and your resting rate is added back. Because a fit person has a lower resting rate, this gives zone targets tailored to their fitness rather than to age alone. Add a resting heart rate and the calculator switches to this method automatically.
The bar is split into five coloured segments, from the easy warm-up zone on the left to the maximal red-line zone on the right. Each segment is labelled with its intensity range and the heart-rate window in beats per minute, so you can see exactly which pulse range each kind of training lives in.
Runners, cyclists, and gym-goers use zones to steer training: easy aerobic base work in the lower zones, threshold and interval work higher up. Fitness watches show your live zone during a workout. If you have a heart condition or are new to intense exercise, check with a doctor before training in the higher zones.