Heart Rate Zone Calculator
Calculate your training zones based on age-predicted max heart rate or a measured max. Use zones to guide cardio intensity for fat loss, aerobic base, or high-intensity conditioning.
Heart Rate Training Zones Explained
Training zones divide your heart rate range into intensity bands, each producing different physiological adaptations. Zone 2 (aerobic base, 60-70% max HR) is where most of your easy training should happen - it builds mitochondrial density and fat-burning efficiency without significant recovery demands. Many endurance athletes spend 80% of their training volume in Zone 2.
Zone 4-5 (threshold and VO2 max, 85-100% max HR) produces the largest cardiovascular adaptations but requires significant recovery. High-intensity intervals should make up no more than 20% of total training volume for most people. More is not better - too much high-intensity work without adequate base aerobic training leads to stagnation and overtraining.
This calculator uses both age-predicted max HR (220 - age) and the Karvonen method with your resting HR to produce both absolute and heart rate reserve-based zones. If you know your actual max HR from a field test or lab, entering it will give more accurate zone calculations than the age-predicted formula.
Frequently Asked Questions
How do I find my true max heart rate?
The most common field test: warm up thoroughly, then run hard up a hill for 2-3 minutes. Sprint as hard as possible for the last 30 seconds. Your heart rate at peak effort is close to your true max. Age-predicted formulas (220 - age) have high individual variability (plus or minus 10-15 bpm) so a measured max is significantly more accurate.
What is Zone 2 training?
Zone 2 is the aerobic base zone - typically 60-70% of max HR. You should be able to hold a conversation but feel like you are working. Zone 2 builds mitochondrial density, improves fat oxidation, and develops aerobic base without significant recovery cost. It is the foundation of endurance fitness and should constitute the majority of cardio for most people.
Should strength athletes do cardio?
Yes. Cardiovascular fitness supports strength training by improving work capacity, recovery between sets, and general health. Low-intensity Zone 2 cardio (30-60 minutes, 2-3x per week) has minimal interference with strength gains and significant health benefits. High-intensity cardio done in excess can interfere with strength adaptation - keep it moderate.
What is the Karvonen method?
The Karvonen formula calculates heart rate reserve zones: Target HR = ((Max HR - Resting HR) x intensity%) + Resting HR. This accounts for your fitness level (reflected in resting HR) and gives more personalised zones than simple percentage of max HR. A fitter person with a lower resting HR will have different absolute zone boundaries at the same percentage.