Karvonen Target Heart Rate Calculator

About this calculator

The Karvonen formula calculates a target heart rate range from heart-rate reserve (HRR) rather than simply taking a percentage of maximum heart rate. HRR is the gap between your maximum heart rate and your resting heart rate, and the formula is: target HR = ((HRmax − HRrest) × intensity%) + HRrest. Because it factors in resting heart rate, it accounts for individual fitness level — two people with the same max HR but very different resting HR get different, more personalized target zones.

Exercise physiologists and personal trainers prefer the Karvonen method over the simpler percent-of-max-HR approach because it is considered more accurate, especially for people who are quite fit (lower resting HR) or deconditioned (higher resting HR). It's commonly used to prescribe cardio intensity zones for interval training, fat-burning zones and endurance-building sessions.

This calculator takes your age (or known max HR), resting heart rate and a target intensity range, and returns the beats-per-minute range you should aim to stay within during exercise.