For general fitness, most guidelines suggest exercising at 50–85% of your max HR. Moderate workouts sit around 64–76%, vigorous workouts around 77–93%. The calculator turns those percentages into bpm for your age.

Including your resting heart rate (the Karvonen method) personalises the zones to your fitness level — a fitter person with a lower resting rate gets different, more accurate targets than the simple percentage-of-max method.

This calculator uses the Tanaka formula — 208 − (0.7 × age) — which is more accurate across ages than the old '220 − age' rule. Your maximum heart rate (max HR) is the basis for all the training zones.

Zones are percentage bands of your max HR, each linked to a training effect: very light recovery, fat-burning/aerobic base, aerobic fitness, anaerobic threshold, and maximum effort. Training in the right zone makes each workout more purposeful.

The Karvonen method personalises zones using your resting heart rate as well as your max HR, giving target = ((max HR − resting HR) × %) + resting HR. If you enter your resting heart rate, the calculator uses this more accurate method.

Use a chest-strap monitor or fitness watch for continuous readings, or pause and count your pulse for 15 seconds and multiply by four. Chest straps are the most accurate for interval training.