Target Heart Rate Calculator
Calculate your target heart rate zones for fat burn, endurance, cardio, and HIIT training. Supports both the Karvonen (heart rate reserve) and age-based percentage formulas so you can train at the right intensity for your goal.
What Is Target Heart Rate?
Target heart rate is the beats-per-minute range you should aim for during exercise to get the benefit you want — whether that is fat burning, endurance building, or peak cardio performance. It is calculated as a percentage of your maximum heart rate (the highest your heart can safely beat during exertion), and training inside the right zone is the single clearest way to match effort to goal. The American Heart Association recommends 50-85% of max heart rate for moderate to vigorous exercise in most healthy adults.
Karvonen vs Percentage Formula
The Karvonen formula uses your heart rate reserve (HRR = max HR minus resting HR) and is considered more accurate because it accounts for fitness level: a fit person with a resting HR of 50 gets different zones than a sedentary person with a resting HR of 80. The formula is: Target HR = ((Max HR − Resting HR) × intensity%) + Resting HR. The percentage method is simpler — just multiply max HR by the intensity (60%, 70%, 85%). It works fine when you don't know your resting heart rate, but underestimates intensity for well-trained athletes.
The Five Heart Rate Zones Explained
Zone 1 (50-60%) is a warm-up / recovery pace — light, conversational. Zone 2 (60-70%) is the classic fat-burning zone and the backbone of endurance training; you can hold a conversation. Zone 3 (70-80%) is aerobic — builds cardiovascular capacity, breathing gets harder. Zone 4 (80-90%) is anaerobic threshold — lactic acid accumulates, this is interval work. Zone 5 (90-100%) is VO2 Max / peak effort — sustainable for only short bursts in HIIT. Most weekly training should be 80% in Zones 1-2 and 20% in Zones 4-5 (the polarized training model).
Which Formula Should You Use?
The classic 220 − age formula is familiar but research (Tanaka 2001) found it overestimates max HR for young adults and underestimates it for older adults. The Tanaka formula (208 − 0.7 × age) is now the preferred default for general use. The Gulati formula (206 − 0.88 × age) was developed specifically from data on women and gives more accurate estimates for female athletes. For the most precision, a graded exercise test with ECG monitoring at a sports lab is the gold standard. If you take beta blockers or have a heart condition, consult your doctor — these formulas do not apply.