Heart Rate Zones Calculator

Which formula does the heart rate zones calculator use?

The Karvonen method: zone heart rate = percentage × (max HR − resting HR) + resting HR. The difference between max and resting is called heart rate reserve. The five zones use 50–60%, 60–70%, 70–80%, 80–90% and 90–100% of that reserve, and every boundary is rounded to a whole beat.

How is max heart rate chosen?

With "Age-based" it uses 220 − age. With "Custom" it uses the number you type. If you pick Custom but leave the value at 0, which is also what a cleared box becomes, the calculator quietly falls back to 220 − age, so check that the Max Heart Rate it displays is the one you meant.

How reliable is 220 minus age?

It is a simple population average and individuals can sit well above or below it, so a 35-year-old’s 185 bpm may be several beats too high or too low for them. If you have a measured max from a supervised test or a recent all-out effort, use Custom. The calculator does not apply other age-based equations.

Why are my zones different from a simple percent-of-max calculator?

The reserve method moves every zone up by your resting rate. With a max of 185 and resting rate of 60, Zone 2 is 135–148 bpm; a plain 60–70% of max would sit lower because it never adds the resting rate back. Whichever method your watch or plan uses, use matching numbers, since the zone labels are not interchangeable across systems.

What happens if resting heart rate is higher than max?

The calculator returns an error that resting heart rate must be lower than max heart rate, rather than showing zones that run backwards. This can happen with a mistyped value or a custom max below your resting rate. A resting heart rate of 0, which is also what a cleared box becomes, is replaced with 60 bpm.

What do the zone names mean here?

They are labels attached to the percentage bands: Recovery, Aerobic Base, Aerobic, Threshold and VO2 Max. The bands are fixed fractions of heart rate reserve, not lab-measured thresholds, so your own lactate or ventilatory threshold may not sit where "Zone 4" does. Heart rate also drifts with heat, caffeine, sleep and fatigue.

Is this suitable if I take heart-rate medication or have a heart condition?

The tool has no way to account for medications such as beta-blockers or for medical conditions, both of which can change heart rate response. Ask your doctor what heart-rate range is appropriate before using these zones. This is general fitness information, not medical advice.