Target Heart Rate Calculator

Enter your age and resting heart rate to calculate moderate and vigorous exercise heart rate zones using the Karvonen formula.

How to Use the Target Heart Rate Calculator

Just two fields — age and resting heart rate — feed the Karvonen formula directly, so the zones below update the instant either number changes.

"Zone 2" and similar training-zone language all trace back to the same underlying idea: exercise intensity, measured as a percentage of how much heart-rate reserve a workout is actually using, not just a raw bpm number that ignores how fit someone already is.

Heart Rate Reserve = Max HR − Resting HR
Target HR = Resting HR + (Reserve × Intensity %)

Max heart rate is estimated here as 220 minus age — a rough population formula with a wide individual error margin, not a measured value. This is the Karvonen formula, named for Finnish physiologist Martti Karvonen, who introduced the heart-rate-reserve method in a 1957 study — and it's a meaningful improvement over just taking a flat percentage of max heart rate alone, because it accounts for resting heart rate, which varies a lot between a sedentary person and a trained endurance athlete.

American College of Sports Medicine (ACSM) guidance frames moderate-intensity exercise as 50-70% of heart rate reserve and vigorous as 70-85%, which is the split shown here. Anyone on heart-rate-affecting medication (beta-blockers especially) should treat the 220-minus-age estimate as unreliable for them specifically — those drugs blunt the heart-rate response these formulas assume is unmedicated.

Not medical advice. These zones are general fitness guidance, not a cardiac assessment. Talk to a doctor before starting a new exercise program, especially with a heart condition, on heart-rate-affecting medication, or after a long period of inactivity.