Heart-rate zone calculator: your five zones, both formulas

Training zones are percentages of a ceiling — and which ceiling formula you use changes the answer. This calculator runs both: the classic 220 − age estimate, and the Karvonen method, which anchors to your heart-rate reserve (max minus resting) and is usually the better fit for trained or older adults. The arithmetic is shown so you can check it. This is general information, not medical advice — if you have a heart condition or are on rate-affecting medication, ask a clinician before using heart-rate targets.

Reading the output

Zone boundaries are conventions, not physiology — different systems shift them a few points either way, and the talk test beats any table when they disagree: comfortable conversation in zone 2, phrases in zone 3, single words in zone 4. The Karvonen column needs your resting heart rate; if you left it blank, only the 220 − age table is shown. Both columns move as fitness improves, because both feed off numbers your training changes. The theory behind every cell of the table is on the heart-rate zones guide; the easy-end training those numbers protect is the zone 2 method.

Sources

• WHO — Physical activity (fact sheet)
• CDC — Physical Activity Basics
• CDC — Target Heart Rate and Estimated Maximum Heart Rate

Every link checked 2026-09-25; sources favour primary and public-health bodies.