How target heart rate zones are calculated
Maximum heart rate (MHR) is estimated from age. Subtracting resting heart rate gives heart rate reserve (HRR) — the Karvonen method then sets each zone as a percentage of HRR added back to resting heart rate.
- MHR — estimated maximum heart rate (Fox & Haskell)
- HRR — heart rate reserve
- intensity — 50–70% fat-burn zone, 70–85% cardio zone
More detail
Why Karvonen instead of a flat percentage of MHR
A simple percentage of max heart rate ignores how fit you already are — two people with the same MHR can have very different resting heart rates. The Karvonen method (1957) factors in resting heart rate via HRR, giving a more personalized target than MHR alone.
Fat-burn vs. cardio zone
The lower-intensity fat-burn zone (50–70% HRR) burns a higher percentage of calories from fat but fewer calories overall per minute. The cardio zone (70–85% HRR) burns more total calories and builds cardiovascular fitness faster. Neither is "better" — they serve different training goals.
Practical tip. Measure resting heart rate first thing in the morning, before getting out of bed, for the most accurate reading. A fitness tracker's real-time heart rate during exercise is more reliable than these estimates once you have one.
Frequently asked questions
What is my maximum heart rate for my age?
The standard estimate is 220 minus your age (Fox & Haskell). Enter your age above for the exact figure — a 30-year-old's estimated max is about 190 bpm.
What heart rate zone burns the most fat?
The fat-burn zone (50–70% of heart rate reserve) burns a higher share of calories from fat, but the cardio zone (70–85%) burns more total calories per minute — neither is strictly "better," they suit different goals. See both zones calculated above from your numbers.
Why use resting heart rate instead of just age?
The Karvonen method factors in your resting heart rate via heart rate reserve (HRR), so two people with the same max heart rate but different fitness levels get different, more personalized target zones than a flat percentage of MHR would give.