Fat Burning Zone Calculator

What Is the Fat Burning Zone?

The "fat burning zone" refers to the exercise intensity at which a higher proportion of calories come from fat oxidation rather than carbohydrate oxidation. This is generally estimated at 60–70% of maximum heart rate ^[1].

It is important to note that while the proportion of fat used as fuel is higher at lower intensities, the total calories burned per minute is lower. Higher-intensity exercise burns more total calories. Both approaches contribute to overall energy expenditure.

Max HR Formulas

• Fox (1971): Max HR = 220 − age. The original and most widely known formula, though it can overestimate for older adults and underestimate for younger adults
• Tanaka (2001): Max HR = 208 − (0.7 × age). Based on a meta-analysis of 351 studies with 18,712 participants. Generally considered more accurate across age groups ^[2]

If you know your actual max heart rate (from a maximal exercise test), enter it in the "Known Max HR" field to override the calculated estimates.

Simple vs. Karvonen Method

The simple method calculates zones as a percentage of maximum heart rate. The Karvonen method uses heart rate reserve (HRR = MaxHR − RestingHR) and adds back the resting heart rate, producing higher BPM targets that account for individual fitness levels.

For a dedicated Karvonen calculator, see our Karvonen Heart Rate Calculator. For cycling-specific zones, try the Cycling HR Zone Calculator.

Individual Variability

Research by Achten & Jeukendrup shows that the intensity at which maximal fat oxidation (FatMax) occurs varies from 25% to 77% of VO2max across individuals ^[3]. Factors including fitness level, training status, genetics, and nutrition all influence fat oxidation rates.

These heart rate zones are general estimates. For precise individual zones, a laboratory-based exercise test with metabolic analysis is the gold standard.

How to Use This Calculator

1. Enter your age
2. Optionally enter your resting heart rate for the Karvonen method
3. Optionally enter a known max HR to override calculated estimates
4. Click "Calculate Heart Rate Zones" to see all zone results

Related tools: Heart Rate Calorie Calculator, Running VDOT Calculator