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Target Heart Rate (Karvonen) Calculator

What should my target heart rate be?

How it is calculated

The Karvonen method works from your heart rate reserve. The tool computes HRmax = 220 − age, then HRR = HRmax − HRrest, then target = HRrest + (intensity/100) × HRR, rounded to the nearest whole beat. Age is in years, resting heart rate in beats per minute (bpm) and intensity in percent of reserve (0 to 100). Because the resting rate is included, two people of the same age get different targets, which a plain percentage of HRmax would not give. The 220 − age estimate of maximum heart rate is only an average and can be off by 10 bpm or more for an individual; medication such as beta blockers also changes heart rate.

Worked example

A 40-year-old with a resting rate of 60 bpm wants to train at 70% intensity. Maximum: 220 − 40 = 180. Reserve: 180 − 60 = 120. Intensity share: 0.70 × 120 = 84. Target: 60 + 84 = 144 bpm. Running the same age at 50% would give 60 + 60 = 120 bpm.

Try this example →

Common mistakes

  • Entering the heart rate measured right after exercise or after coffee instead of the true resting rate (take it on waking, at rest).
  • Entering intensity as a decimal such as 0.7; the field expects a percent (70).
  • Treating the result as a percentage of maximum heart rate; it is a percentage of reserve, so values differ.
  • Treating 220 − age as exact, when it can be well off for some people.
  • Ignoring medical advice when taking heart-rate-affecting medication or having a heart condition.

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.

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