How it works
Estimated maximum heart rate uses the simple, widely cited 220 − age formula. Training zones then use the Karvonen method, which factors in resting heart rate as well — two people with the same max heart rate but very different fitness levels (and so very different resting rates) get meaningfully different target zones, which a max-heart-rate-only method would miss.
max HR = 220 − age
heart rate reserve (HRR) = max HR − resting HR
target HR = (HRR × intensity%) + resting HR
Worked example
Age 40, resting heart rate 70 bpm.
- Max HR = 220 − 40 = 180 bpm.
- HRR = 180 − 70 = 110 bpm.
- Moderate zone (70–80%): 110 × 0.70 + 70 = 147, 110 × 0.80 + 70 = 158.
The moderate ("cardio") zone for this profile is 147–158 bpm, and every other zone follows the same pattern up to the maximum zone, which tops out exactly at max HR (180 bpm) — a useful check on the arithmetic.
Common questions
How accurate is "220 minus age"?
It's a population average with a fairly wide error margin (± 10–12 bpm) for any one person — some more recent formulas (like Tanaka's 208 − 0.7 × age) try to correct for a slight bias in older adults, but no age-only formula replaces an actual measured max heart rate from a supervised fitness test.
Why use resting heart rate at all?
Two people can share a max heart rate but have very different resting rates — a fitter heart rests lower. The Karvonen method's heart rate reserve captures that difference, giving each person zones scaled to their own range rather than a flat percentage of max HR alone.
Which zone should I train in?
It depends on the goal: light-to-moderate zones build an aerobic base and are sustainable for longer sessions, while hard and maximum zones build speed and power but can only be sustained briefly. Most training plans spend the majority of time in the lighter zones.