When it comes to fitness and exercise programs, not only can staying within your target heart rate zone help you to get better results more quickly, it can help you to prevent serious injury. There are many heart rate calculators that you can use to determine your target heart rate, but taking a couple extra minutes to compare the results to the Karvonen Formula is worth the time.

Most online calculator will give you slightly different results than the ones you find below. They may have a more simple formula or rely on an outdated and less accurate formula for calculating your Maximum Heart Rate. Or there may be other reasons. Either way when it comes to your health it pays to compare results and always check with your physician before starting or modifying any exercise program (see the special note on medications below).

Karvonen Formula

The Karvonen Formula is a mathematical formula that helps you determine your target heart rate zone. The formula involves using your maximum heart rate (MHR) minus your age to come up with a target heart rate range (which is a percentage of your MHR). Staying within this range will help you work most effectively during your cardio workouts.

Below is an example of the Karvonen formula for a 47 year old with a resting heart rate of 65 beats per minute. Whenever we got percentages, we rounded down for an added measure of safety.

First Calculate your maximum heart rate (MHR).
206.9 - (0.67 x 47 (age) = 175 MHR

Your maximum heart rate (MHR) is the fastest rate at which your heart should ever beat in one minute. Do NOT exceed this amount. And if you approach it, you’re working too hard and need to slow down immediately.

MHR - resting heart rate (RHR) = 110

To get your resting heart rate, take your pulse for 15 seconds and multiply by 4, after you've been resting for a while. The most accurate way would be to count all the way through for a whole minute.

Determine Your Target Heart Rate Zone

• 110 * 65% (.65, low end of heart rate zone)
• 110 * 85% (.85, high end of heart rate zone) = 71 OR 93
• 71 + 65 (RHR) = 136
• 93 + 65 (RHR) = 158

The target heart rate zone for this person would be 137 to 159. Please note, these calculations are a little higher than most online calculators. We provided some links below for your convenience.

How hard you work while exercising can make a big difference in how many calories you burn and your ability to build stamina and endurance. Staying within your target heart rate zone can help you maximize your effort in the safest way possible.

Exercise Resources:

Mayo Clinic Heart Rate Calculator

Using the Body Mass Index

Setting Exercise Goals and Exercise Worksheets

About.com's Heart Rate Calculator

Note: Several types of medications can lower your maximum heart rate and, therefore, lower your target heart rate zone. Beta blockers, most anti-arrhythmic medications, some calcium blockers and digoxin are among the most common. In some people, H-2 blockers prescribed for acid reflux also reduce maximum heart rate. If you're taking any of these medications, ask your doctor if you need to use a lower target heart rate.