Find your Zone 2 heart rate.
Two inputs, no email address. Your age gives an estimated max; your resting heart rate — if you know it — personalizes the range.
Estimates only — formulas miss real max heart rates by 10+ bpm for plenty of people. The honest caveats are below the math.
208 − (0.7 × age) — from Tanaka, Monahan & Seals (2001), a meta-analysis of 351 studies validated in the lab. It outperforms the older 220 − age rule, especially past middle age.
60–70% × max — the Zone 2 band in the common five-zone model, per the Cleveland Clinic. Threshold-anchored systems used in elite sport put “zone 2” higher, so always name your model.
(max − rest) × 60–70% + rest — the Karvonen method, which folds your resting heart rate in. It usually lands higher than the straight percentage, and fitter hearts get more personal numbers.
Treat the number as a starting point.
Age formulas carry a standard error of roughly 7–11 bpm, and the physiological boundaries of Zone 2 vary by more than 20% between individuals — so any fixed percentage misses for many people. Cross-check with the talk test — comfortable speech sits at or below the first ventilatory threshold — and if you want real precision, the gold standard is a stress test or VO2 max test.
Or skip the arithmetic: Apple Watch already builds personalized zones from your health data, and Zone2 reads them straight from Health. How to find your zones →
Now hold that range.
Zone2 is free. Your watch shows the zone you're in while you train, and every workout gets scored against the range you were aiming for.