Fat Burning Zone Calculator

The fat burning zone is the exercise intensity range — typically 60% to 70% of your maximum heart rate — at which your body preferentially uses stored fat as its primary fuel source. At lower intensities, fat metabolism is more efficient than carbohydrate metabolism, making this zone ideal for steady, sustainable fat loss.

The most widely used formula is MHR = 220 − age. For example, a 35-year-old has an estimated MHR of 185 bpm. This is an estimate; your actual MHR may vary based on genetics, fitness level, and health status. A supervised stress test provides the most accurate measurement.

Your fat burning zone sits between 60% and 70% of your maximum heart rate. For a 35-year-old with an MHR of 185 bpm, this is roughly 111–130 bpm. Staying within this range during aerobic exercise encourages your body to oxidise fat rather than rely heavily on carbohydrates.

The Karvonen (heart rate reserve) method factors in your resting heart rate for a more personalised target: THR = ((MHR − RHR) × % intensity) + RHR. Because fitter individuals often have lower resting heart rates, this formula accounts for cardiovascular conditioning and produces a more accurate training zone than the simple percentage-of-MHR approach.

Zone 2 typically corresponds to 60–70% of your maximum heart rate, which closely overlaps with the fat burning zone. It is a conversational, aerobic pace where you can sustain exercise for long periods. Zone 2 training is popular for endurance athletes and those focused on metabolic health and fat oxidation.

The fat burning zone (60–70% MHR) burns a higher proportion of calories from fat but at a lower total calorie burn per minute. The cardio zone (70–85% MHR) burns more total calories per minute but relies more on carbohydrates. For pure fat loss, either can be effective; the fat burning zone is simply more comfortable and sustainable for longer sessions.

Low-to-moderate intensity activities work best: brisk walking, light jogging, cycling at a steady pace, swimming laps, and using an elliptical trainer. The key is to keep your heart rate consistently in the 60–70% MHR range rather than spiking it with high-intensity bursts.

The most convenient options are a chest strap heart rate monitor (most accurate), a fitness tracker or smartwatch, or a gym machine's built-in grip sensors. You can also estimate manually: count your pulse for 15 seconds and multiply by 4. Aim to check periodically throughout your workout to stay within your target zone.