What Is the Fat Burning Zone?
The fat burning zone refers to a heart rate range, generally 60 to 70 percent of your heart rate reserve, where the body draws a relatively higher proportion of its energy from fat stores during steady, moderate-intensity exercise.
The Formula
This calculator uses the Karvonen method: first, estimated Max Heart Rate = 220 – Age. Then Heart Rate Reserve (HRR) = Max Heart Rate – Resting Heart Rate. The fat burning zone is Resting Heart Rate + (60% to 70% × HRR).
Important Context
While this zone burns a higher percentage of calories from fat, higher-intensity exercise generally burns more total calories (and often more total fat) per minute. Heart rate zones are useful training guides but are general estimates, not precise metabolic measurements, and are provided for general fitness planning purposes.