Your zones are personal. Here’s how to find them.
Every zone is a slice of your maximum heart rate, so the whole system leans on one number — and the formula everyone knows for that number is the weakest part. Here’s how to do better, in three steps.
Estimate your max heart rate — skeptically.
The famous “220 minus age” formula was never derived from original research — it traces to a 1971 paper that eyeballed a line through earlier studies, and its estimates commonly miss real max heart rates by 10 or more beats per minute.
A better default comes from Tanaka, Monahan & Seals, who pooled 351 studies and then validated the result in the lab: 208 − (0.7 × age). The same paper found the relationship holds for both sexes regardless of fitness level — and that 220 − age underestimates the max of older adults, which quietly sets their zones too low.
Slice it into five zones.
In the most common five-zone model, each zone is a band of your max: Zone 2 is 60–70% of max heart rate, with recovery below it and tempo, threshold, and peak efforts stacked above.
If you know your resting heart rate, the heart-rate-reserve (Karvonen) method refines this: take the same percentages of the gap between resting and max, then add your resting rate back. Two people with the same max but different resting rates get different — more personal — zones.
Sanity-check against your body.
Formulas are population averages, and individuals scatter widely around them — one recent analysis found the physiological boundaries of Zone 2 vary by more than 20% between people, so any fixed percentage will be wrong for many. The most accurate way to know your max is an exercise stress test or VO2 max test.
Short of a lab, use the talk test: research on speech during exercise shows comfortable speech sits at or below the first ventilatory threshold — the ceiling of easy aerobic work. If your “Zone 2” number leaves you gasping, your zones are set too high, no matter what the formula said.
Or let your devices do it — then check their work.
If you use an Apple Watch, your zones are already there: Apple calculates five personalized zones automatically from your health data, and you can edit zones 2–4 by hand in Settings → Workout → Heart Rate Zones. Zone2 reads whatever is in Health — automatic or hand-tuned — and scores every workout against it.
Zones set. Now hit them.
Zone2 is free. It reads your zones straight from Apple Health, scores every workout against them, and shows you the minutes that counted.