Heart Rate Zone Calculator
Personalized cardio zones using age and resting heart rate (Karvonen formula).
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Heart rate training zones let you exercise at the right intensity for the right purpose. Training too easy, you get minimal cardiovascular benefit; too hard, you accumulate fatigue without proportional gain. This calculator uses the Karvonen formula — which accounts for your resting heart rate, not just your maximum — to give you personalised zones for fat burning, aerobic conditioning, and high-intensity intervals.
Example
Resting HR: 58 bpm Estimated max HR: 185 bpm
Karvonen Formula
Zone 2: 60–70%
Why Karvonen Is More Accurate Than Age-Based Formulas
The simple formula (220 − age) estimates max HR but ignores cardiovascular fitness. The Karvonen formula uses Heart Rate Reserve (HRR = max HR − resting HR) because resting HR reflects fitness level. A fit 40-year-old with a resting HR of 48 has different zones than a sedentary 40-year-old with a resting HR of 75 — even with the same max HR. For best results, use an actual max HR test rather than the 220-age estimate.
Frequently Asked Questions
Which zone is best for fat loss?
Zone 2 (60–70% HRR) burns the highest proportion of fat as fuel, but higher zones burn more total calories. Both are useful.
How do I find my true maximum heart rate?
A graded exercise test (ramp test) or a supervised field test (e.g., 3km time trial) gives the most accurate reading. Age formulas have ±10–12 bpm error.
What is Zone 2 training and why is it popular?
Zone 2 (aerobic base) improves mitochondrial density, fat oxidation, and recovery capacity. It's the foundation of most elite endurance training plans.
How do I measure heart rate during exercise?
A chest strap monitor is most accurate. Wrist-based optical monitors are convenient but can read 5–15 bpm high during intense intervals.