Heart Rate Zone Calculator

HRmax = 220 − age (or your measured max). %HRmax zones apply each percentage to HRmax. Karvonen: target = intensity × (HRmax − HRrest) + HRrest.

Karvonen MJ, Kentala E, Mustala O (1957); Fox & Haskell HRmax estimate.

The 220 − age estimate carries a ±10–12 bpm spread. A measured HRmax and resting heart rate make the zones substantially more accurate.

People on heart-rate-altering medication (such as beta-blockers) or with cardiac conditions — train to zones set with a clinician.

By default we take a percentage of your estimated maximum heart rate (220 minus your age) for each of five zones. If you enter a resting heart rate, we switch to the Karvonen method, which works from your heart-rate reserve for more personal numbers.

%HRmax applies each zone percentage directly to your max heart rate. Karvonen uses heart-rate reserve — the gap between your max and resting rates — which accounts for fitness. Fitter people with low resting rates get meaningfully different zone boundaries under Karvonen.

Zone 2 is the aerobic base: an easy, conversational effort you can sustain for a long time. Training here builds mitochondria and fat-burning capacity while keeping fatigue low, which is why endurance coaches want most weekly volume in this zone.

It's a population average with a spread of roughly 10–12 beats either way, so an individual's true max can differ noticeably. A measured max from a hard field test or lab makes every zone more accurate; enter it directly if you have it.

No. A common model is roughly 80% of training easy (zones 1–2) and 20% hard (zones 4–5), with less time in the middle. The easy volume builds the engine; the hard sessions sharpen the top end.