Fat Burning Zone Calculator
Use the Karvonen Formula for optimal accuracy
How to Find Your Optimal Fat Burning Zone
Identifying your target heart rate is crucial for maximizing the efficiency of your workouts. While high-intensity interval training (HIIT) has its place, working out in the specific "Fat Burning Zone" (Zone 2) is often cited as the most effective way to utilize stored fat for energy rather than carbohydrates. This calculator uses the Karvonen Formula, which is widely considered more accurate than simple age-based formulas because it factors in your resting heart rate.
What is the Karvonen Formula?
Unlike the standard "220 minus age" equation, the Karvonen method accounts for your individual fitness level by incorporating your Resting Heart Rate (RHR). The formula works as follows:
- MHR (Max Heart Rate): 220 – Age
- HRR (Heart Rate Reserve): MHR – RHR
- Target Heart Rate: (HRR × Intensity %) + RHR
Understanding the Heart Rate Zones
Zone 1 & 2 (Fat Burning – 60-70% Intensity):
This implies moderate intensity. Your body works efficiently enough to use fat as its primary fuel source. Breathing is heavier than normal, but you should still be able to carry on a conversation. This is ideal for weight loss and endurance building.
Zone 3 (Aerobic – 70-80% Intensity):
This zone improves your cardiovascular system and respiratory health. While you still burn fat here, the percentage of calories burned from fat decreases as the body switches to glucose for faster energy.
How to Measure Your Resting Heart Rate
To get the most accurate result from the calculator above, measure your heart rate immediately after waking up in the morning, before getting out of bed. Count your pulse for 60 seconds (or 15 seconds and multiply by 4). Do this for three consecutive days and take the average.