Target Heart Rate Calculator

This target heart rate calculator tells you which heart-rate ranges to aim for during exercise so each workout actually does what you want it to do. Your heart rate is the clearest real-time signal of how hard you are working: too easy and you may not improve, too hard for too long and you risk burnout or injury. By converting your age (and optionally your resting heart rate) into personalised beats-per-minute (bpm) zones, the tool lets you train with purpose rather than guesswork.

It is for anyone who exercises with a smartwatch, fitness band, or chest strap — walkers and joggers wanting an easy "fat burn" pace, gym-goers building cardio endurance, and runners or cyclists doing interval training in the high-intensity zone. Enter your age, optionally your resting heart rate, and (if you like) your current bpm to instantly see which zone you are in right now.

Maximum heart rate — the 220 − Age formula

The calculator first estimates your maximum heart rate (MHR), the fastest your heart can safely beat, using the long-standing formula MHR = 220 − age. It then carves that maximum into three training zones as percentages of MHR: Fat Burn 50–65%, Cardio 65–85%, and Peak / HIIT 85–100%. This estimate is convenient but approximate — individual maximums vary by roughly ±10–12 bpm, so treat the numbers as a guide rather than a hard limit. A supervised VO2 max test or ramp test gives a truer personal maximum.

The Karvonen method (more accurate)

If you know your resting heart rate (RHR), switch on the Karvonen method for a more individualised result. It is based on your Heart Rate Reserve (HRR = Max HR − Resting HR), the working range between rest and maximum, and computes each zone as Target = RHR + (HRR × intensity%). Because a fitter person with a low resting heart rate has a wider reserve, Karvonen tailors the zones to your conditioning instead of treating everyone of the same age identically.

Worked example

For a 30-year-old, the maximum heart rate is 220 − 30 = 190 bpm. The simple-percentage cardio zone (65–85%) is 0.65 × 190 to 0.85 × 190, or roughly 124–162 bpm. Now apply Karvonen with a resting heart rate of 65 bpm: the reserve is 190 − 65 = 125 bpm, so the cardio zone becomes 65 + (125 × 0.65) to 65 + (125 × 0.85), or about 146–171 bpm. Notice the Karvonen range sits a little higher — that is the personalisation at work, since it accounts for the fact that your heart never actually drops to zero.

Tips for using your zones

For general health, the World Health Organization suggests 150 minutes of moderate (cardio-zone) activity a week, which you can split across most days. Spend the bulk of your easy sessions in the fat-burn and lower-cardio zones and reserve short bursts for the peak zone. A chest strap reads more accurately than a wrist optical sensor for interval work. Recheck your zones after a few months of consistent training — as fitness improves, your resting heart rate usually falls, which widens your reserve and shifts your Karvonen zones.

Common mistakes

Believing 220 − age is exact is the classic error; it is an average, and your true maximum can be more than 10 bpm higher or lower. Living in the peak zone is another — high-intensity work is meant for short intervals, not whole sessions, and overdoing it invites fatigue and injury. Many people also assume the "fat burn" zone burns the most fat overall; it burns a higher percentage of fat but fewer total calories than the cardio zone, so for fat loss the total calories you burn matter more than the label. Finally, wrist-based readings can lag or misread during fast intervals, so do not chase a number your watch may be reporting late.