Target Heart Rate (Karvonen) Calculator

About this calculator

This tool calculates a personalized target heart rate zone for exercise using the Karvonen formula, which factors in resting heart rate alongside age and desired intensity — unlike simpler age-only formulas, this accounts for individual fitness level, since two people the same age can have very different resting heart rates depending on how fit they are. It first estimates heart rate reserve (max heart rate minus resting heart rate), then scales that reserve by the chosen intensity percentage and adds resting heart rate back in.

It is used by runners, cyclists and gym-goers who want to train at a specific intensity — for example staying in a fat-burning or cardio zone rather than going all-out — and by personal trainers setting workout intensity targets for clients. Because it's more personalized than flat percentage-of-max-heart-rate formulas, the Karvonen method is generally preferred by anyone tracking heart rate on a fitness watch or chest strap during structured training.