The Karvonen formula
Unlike the simple "220 − age" calculation used alone, the Karvonen formula (also called the heart rate reserve method) also factors in your resting heart rate — the more cardiovascularly conditioned you are, the lower your resting HR tends to be, and the formula adjusts your training zones to reflect that, instead of using the same range for everyone of the same age.
How to measure resting heart rate
The most accurate way is to measure your pulse (or use a heart rate monitor) right when you wake up, while still lying down, before getting out of bed — even light activity already raises heart rate. Typical values range from 60-100 bpm, with well-conditioned athletes often below 60 bpm.
These zones are general estimates — people with heart conditions or taking medication that affects heart rate (like beta blockers) should follow specific medical guidance, not this calculator.
Frequently asked questions
Which zone should I train in to lose weight?
The "fat burn" zone (60-70% of reserve) uses proportionally more fat as fuel, but the "aerobic" zone (70-80%) burns more total calories per minute — for weight loss, total calories burned over the week matters more than the specific zone of any one session.
Wouldn't the "220 − age" formula be simpler?
It's simpler, but less accurate — it completely ignores your individual fitness level (resting HR), treating an athlete and a sedentary person of the same age as if they had exactly the same cardiovascular capacity, which is rarely the case.