Why is Zone 2 Cardio so important for weight loss and longevity?

In Zone 2, your body primarily uses fat as fuel (fat oxidation) rather than carbohydrates. This metabolic state improves insulin sensitivity, mitochondrial efficiency, and can be sustained for long durations without fatigue, leading to higher total calorie burn over time.

Target Heart Rate Zone Calculator (Karvonen)

Why the Karvonen Formula is Superior

Most basic gym machines use the standard 220 - Age formula to estimate your zones. The problem? It ignores your individual fitness level.

The Karvonen Formula factors in your Resting Heart Rate (RHR). A fit person has a lower RHR (e.g., 50 bpm) compared to an average person (70 bpm). This gives the fit person a larger "Heart Rate Reserve" to train in. By accounting for this reserve, the Karvonen method provides training zones that are much more accurate to your actual metabolic state.

Understanding the 5 Zones

60-70% Zone 2: The Goldilocks Zone

This is where longevity lives. It builds mitochondria, burns pure fat for fuel, and improves your "metabolic flexibility." You should be able to hold a conversation in this zone. It's not easy, but it shouldn't be exhausting.

90-100% Zone 5: VO2 Max

Pure agony. This zone is for short intervals (1-4 minutes) to increase your VO2 Max, which is the ceiling of your aerobic performance. It is highly taxing on the nervous system and requires ample recovery.

Frequently Asked Questions

Why is Zone 2 Cardio so important?

In Zone 2, your body primarily uses fat oxidation as its fuel source rather than glycolytic (carb) energy. This metabolic state drastically improves insulin sensitivity and mitochondrial efficiency. Unlike HIIT, which creates high systemic fatigue, Zone 2 can be performed comfortably for longer durations, leading to higher total calorie burn over time without burnout.

How do I measure my Resting Heart Rate accurately?

The most accurate reading is taken immediately upon waking, before you sit up, check your phone, or drink coffee. Wearables (Apple Watch, Garmin, Whoop) track this automatically, but you can also count your pulse at the neck for 60 seconds manually. A lower number (e.g., 40-50 bpm) generally indicates a highly efficient "Athlete's Heart."

What if my Max Heart Rate feels higher than 220 minus age?

The `220 - Age` formula is a population average. Many individuals have a genetic max HR that varies by +/- 10-15 beats. If you regularly see a higher number on your heart rate monitor during all-out sprint intervals, use that observed maximum instead of the calculated one for better zone accuracy.

Should I use this if I am on Beta-Blockers?

Medical Warning: No.Beta-blockers artificially lower your heart rate. Standard formulas will not apply to you. You should consult your cardiologist for a "Rate of Perceived Exertion" (RPE) scale instead of relying on BPM numbers.

Tools & Data Verified by the EverydayCalculators Medical Research Team.

Last updated: January 2026.

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Target Heart Rate Calculator

Why the Karvonen Formula is Superior

Understanding the 5 Zones

60-70% Zone 2: The Goldilocks Zone

90-100% Zone 5: VO2 Max

Frequently Asked Questions