Health and fitness tools
Heart Rate Zone Calculator
Calculate your five Karvonen heart rate training zones from age and resting heart rate locally in your browser.
Enter your age and resting heart rate (measured after sitting quietly for a few minutes) to see your five Karvonen training zones. The calculator uses 220 − age for maximum heart rate and applies the heart-rate-reserve method. The calculation runs locally in your browser; your values are not uploaded or stored.
Find your personal training zones for more effective workouts.
Enter your age and resting heart rate to see your five heart rate zones based on the Karven formula (heart rate reserve method). Zone 1 is very light for recovery, Zone 2 is light for fat burning and endurance, Zone 3 is moderate for aerobic fitness, Zone 4 is hard for threshold training, and Zone 5 is maximum for VO2 max intervals. Maximum heart rate uses the common 220 − age estimate; actual max may vary. This is a general fitness estimate, not medical advice; your values are calculated locally and are not uploaded or stored.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
How does the heart rate zone calculator work?
Enter your age and resting heart rate. The calculator estimates your maximum heart rate as 220 − age, then calculates heart rate reserve (max − resting). Each zone is a percentage of that reserve added to your resting heart rate using the Karvonen formula: target = resting HR + reserve × intensity.
What are the five training zones?
Zone 1 (50–60%): Very light, recovery and warm-up. Zone 2 (60–70%): Light, fat burning and endurance base. Zone 3 (70–80%): Moderate, aerobic fitness. Zone 4 (80–90%): Hard, threshold and lactate tolerance. Zone 5 (90–100%): Maximum, VO2 max and speed intervals.
Why use heart rate reserve instead of just max heart rate?
The Karvonen formula accounts for your resting heart rate, giving more personalized zones than using a straight percentage of max heart rate. Two people with the same age but different resting heart rates will get different zone ranges.
Is the 220 − age formula accurate for everyone?
No. 220 − age is a population estimate; your actual maximum heart rate can be 10–20 beats higher or lower. For precise zones, use a lab-tested max or a field test under medical supervision. This calculator is a general fitness estimate, not medical advice.
Do my values leave my browser?
No. The calculation and copy action run locally in your browser. CodeASystem does not upload or store the age or resting heart rate you enter.