Target Heart Rate Calculator
This free target heart rate calculator turns your age — and optionally your resting heart rate — into five training zones in beats per minute: warm-up, fat burn, aerobic, anaerobic, and maximum. Enter a resting heart rate and it uses the Karvonen formula, which personalizes zones using your heart-rate reserve instead of age alone. Everything runs in your browser.
How the Zones Are Calculated
First your maximum heart rate is estimated with the classic 220 − age rule or the Tanaka formula (208 − 0.7 × age), or you can enter a measured HRmax from a fitness test. With a resting heart rate, each zone is computed as (HRmax − resting HR) × intensity + resting HR — the Karvonen method. Without one, zones fall back to simple percentages of HRmax. The five zones span 50–100% intensity in 10-point steps.
The Fat-Burn Zone, Honestly
Zone 2 (60–70%) is called the fat-burning zone because at that intensity the highest proportion of energy comes from fat. Harder efforts still burn more total calories per minute, so for weight loss the zone that matters most is the one you can sustain consistently. Zone 2 is also where endurance athletes build their aerobic base — comfortable, conversational effort you can repeat day after day.
Using Your Zones in Training
A practical weekly pattern for general fitness: most sessions in Zone 2, some steady work in Zone 3, and one or two harder sessions touching Zone 4. Zone 5 is for short intervals only. If you take medication that affects heart rate (such as beta blockers) or have a cardiac condition, formula-based zones do not apply — get guidance from a clinician instead.