Fat Burning Zone Calculator — What It Really Means
Calculate your five heart rate training zones from age using the Tanaka formula, with optional Karvonen (heart rate reserve) targets from your resting pulse.
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About this tool
This page opens the heart rate zone calculator with the low-intensity band highlighted — the range that gym equipment likes to label the fat burning zone.
Honest context: the fat burning zone is a marketing name for easy zone 2 exercise. At low intensity a higher percentage of the calories you burn comes from fat, which is true — but the total calories per minute are lower, so a harder session can burn more fat in absolute terms. No heart rate range melts fat by itself; the energy balance over days does.
That said, the zone is genuinely useful: it is sustainable for long sessions, easy to recover from and a solid default for beginners. Compute yours from age here, and add resting heart rate for the more personal Karvonen version.
Example. Age 40 produces a Tanaka maximum of 180 bpm and a classic maximum of 180 bpm, with zone 1 at 90 to 108 bpm.
Limit. Age must be from 10 to 100, and a resting heart rate, if entered, must be from 30 to 120.