A worked example
A 35-year-old with a resting heart rate of 65 bpm has an estimated max heart rate of 185 bpm — putting the "cardio" zone (70-80% intensity) at roughly 149-161 bpm.
Frequently asked questions
Why use Karvonen instead of just a % of max heart rate?
The simple % method ignores how fit you already are. Karvonen factors in your resting heart rate too — two people with the same max heart rate but very different resting rates (often reflecting different fitness levels) get meaningfully different target zones.
How do I find my actual resting heart rate?
Check your pulse first thing in the morning before getting out of bed, ideally over a few days for an average — it's most accurate when you're truly at rest, not right after waking from an alarm.
Is 220 minus age my actual max heart rate?
It's a population-average estimate with a real spread between individuals — a fitness watch or supervised exercise test would give you your real number, but this formula is a reasonable starting point for most training purposes.
This calculator provides estimates for general informational purposes only and is not medical advice. Consult a doctor before starting a new exercise program, especially with any heart condition.