What is the Fat Burning Zone?

The 'Fat Burning Zone' is typically 60-70% of your maximum heart rate. In this lower-intensity zone, your body relies primarily on fat stores for fuel. However, you burn fewer total calories per minute than in high-intensity zones.

What is Max Heart Rate (MHR)?

The simplest formula is 220 minus your age. If you are 30 years old, your estimated MHR is 190 beats per minute (bpm). More complex formulas (like Tanaka: 208 - 0.7 × age) exist for greater accuracy.

Is higher heart rate always better?

No. Staying at peak heart rate (90-100%) for too long can be dangerous and lead to burnout or injury. Most efficient training occurs in Zones 2 (Endurance) and 4 (Threshold).

How do I calculate heart rate reserve?

Heart Rate Reserve (HRR) = Max Heart Rate (MHR) - Resting Heart Rate (RHR). This number represents the total range your heart can operate in. The Karvonen Formula uses HRR to calculate more accurate zones for fit individuals.

Master Your Heart Rate Zones

Work smarter, not harder. Most people train in the "Black Hole" zone—too hard to recover, but too easy to create positive adaptation. Tracking your heart rate fixes this.

Calculate Your Zones

Don't guess your bpm. Use our calculator to find your exact numbers for Fat Burn vs Cardio.

Check Health Stats

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The 220 Formula vs. Karvonen Formula

Most gym machines use the simple "220 - Age" formula. It's okay for beginners, but it ignores your fitness level.

The Better Way (Karvonen):People with a low Resting Heart Rate (RHR) represent higher fitness. The Karvonen formula uses "Heart Rate Reserve" to customize the intensity.
Formula: Target HR = ((Max HR − Resting HR) × %Intensity) + Resting HR

The 5 Heart Rate Zones Explained

Every zone serves a specific metabolic purpose. If you mix them up, you lose specific benefits.

Zone 1: Very Light (50-60%)

Feeling: Very easy breathing. You can sing a song.
Purpose: Warm-ups, cool-downs, and "Active Recovery" days. It promotes blood flow to help muscles repair without adding stress.

Zone 2: The Endurance Zone (60-70%)

The "Fat Max" Zone.
Feeling: You can hold a conversation, but you'd rather not debate philosophy. Sweating lightly.
Purpose: This is where mitochondrial efficiency happens. Your body teaches cells to burn fat for fuel. Endurance athletes spend 80% of their training here.

Zone 3: The Aerobic Zone (70-80%)

The "Grey Zone".
Feeling: Moderate strain. Speaking in short sentences.
Purpose: Improves blood circulation and skeletal muscle strength. However, many runners get stuck here—it's too hard to build endurance volume, but too easy to build speed. Use sparingly.

Zone 4: The Threshold Zone (80-90%)

The "Burn" Zone.
Feeling: "Comfortably hard." Your muscles start to burn as lactic acid builds up. You can only speak a few words at a time.
Purpose: Increases your Anaerobic Threshold (how long you can run fast). This is race pace.

Zone 5: The Maximum Zone (90-100%)

All Out Effort.
Feeling: Gasping for air. Cannot talk. Vision tunnels.
Purpose: Max speed and neuromuscular power. Only sustainable for 30 seconds to 2 minutes. Used in HIIT intervals.

The Talk Test (No Monitor Needed)

Forgot your Apple Watch? Use your mouth.

Zone 1-2: Can speak in full paragraphs.
Zone 3: Can speak in full sentences, but need to breathe between them.
Zone 4: Can speak 3-4 words ("I'm... doing... okay").
Zone 5: Cannot speak. Grunt only.

The Fat Burning Myth

Gym machines label Zone 2 as the "Fat Burning Zone." This is misleading.

True: In Zone 2, a higher percentage of fuel comes from fat (vs carbs).
Also True: In Zone 4/5, you burn MORE total calories.

Example:
30 mins Zone 2: 200 calories (160 from fat).
30 mins Zone 4: 400 calories (120 from fat).

For weight loss, total calorie deficit matters most. But Zone 2 is magical because you can do it for hours without burnout, whereas Zone 4 fries your nervous system quickly.

Conclusion

Stop training in the "Grey Zone" (Zone 3) every day. Adopt a Polarized Approach: Spend 80% of your time in Zone 2 to build a massive engine, and 20% in Zone 5 to build a turbocharger.