How to Use the Fat-Burning Heart Rate Zone Calculator
Enter your age and resting heart rate to calculate personalized heart rate zones using the Karvonen formula. The fat-burning zone (60–70% HRR) is where your body uses fat as its primary fuel source during exercise.
Karvonen Formula
Max HR = 220 − age
Heart Rate Reserve (HRR) = Max HR − Resting HR
Target HR = HRR × intensity % + Resting HR
The Karvonen method is more accurate than simple max-HR percentage because it factors in your individual fitness level via resting heart rate.
Heart Rate Zone Guide
60–70% (Fat-Burning): Walking, light jogging. Highest fat-to-carb burn ratio, sustainable for long sessions.
70–80% (Aerobic): Moderate running. Improves cardiovascular fitness and endurance.
80–90% (High-Intensity): Fast running, HIIT. Burns more total calories, but carbohydrates become the primary fuel.
Tips for Fat-Burning Cardio
Aim for at least 30 minutes in the fat-burning zone per session. Exercising 3–5 times per week at 40–60 minutes each is optimal. A lower-intensity, longer-duration approach is especially effective for beginners or those returning from injury.
Frequently Asked Questions
Not necessarily. High-intensity training burns more total calories, which can result in greater overall fat loss. The fat-burning zone is ideal for beginners, steady-state cardio, and active recovery days.
It's a convenient estimate, but individual variation is large. The Tanaka formula (208 − 0.7 × age) is slightly more accurate for adults. For true max HR, a supervised graded exercise test is the gold standard.