The Karvonen Formula: Calculate Your Target Heart Rate

Understanding the Karvonen Formula for Target Heart Rate

The Karvonen formula, also known as the heart rate reserve (HRR) method, is a widely used equation to calculate your target heart rate zones for exercise. Unlike simple percentage-based methods that rely only on maximum heart rate, the Karvonen formula incorporates your resting heart rate, making it more personalized and accurate. This deep dive explains how the formula works, why it matters, and how to apply it to your training.

The Formula

The Karvonen formula is expressed as:

Target HR = ((Max HR − Resting HR) × Intensity %) + Resting HR

Where:

• Max HR (Maximum Heart Rate): The highest number of beats per minute your heart can achieve during maximal exertion. A common estimate is 220 − Age for men and 226 − Age for women. (The calculator on our site uses this adjustment.)
• Resting HR (Resting Heart Rate): Your heart rate when you are fully awake but at rest, ideally measured first thing in the morning before getting out of bed.
• Heart Rate Reserve (HRR) = Max HR − Resting HR. This is the range between your resting and maximum heart rates.
• Intensity %: The desired exercise intensity as a decimal (e.g., 0.65 for 65%). Common zones start at 50% for light activity up to 90% for high-intensity training.

Example Calculation

Suppose a 35-year-old woman has a resting heart rate of 68 bpm and wants to exercise at 70% intensity:

• Max HR = 226 − 35 = 191 bpm
• HRR = 191 − 68 = 123 bpm
• Target HR = (123 × 0.70) + 68 = 86.1 + 68 = 154.1 bpm (rounded to 154 bpm)

Why the Karvonen Formula Works

The formula is based on the concept of heart rate reserve — the difference between your maximum and resting heart rates. This reserve represents the capacity your heart has to increase its rate during exercise. By adding a percentage of that reserve back to your resting rate, you get a target heart rate that reflects your current fitness level. For example, a person with a lower resting heart rate (indicating better fitness) will have a larger reserve and therefore a lower target heart rate for the same intensity, because their heart is already more efficient. This makes the Karvonen formula more accurate than methods that rely solely on maximum heart rate percentages.

Historical Origins

The formula was developed by Finnish physiologist Dr. Martti Karvonen in the 1950s. Karvonen was studying the relationship between heart rate and exercise intensity, and he proposed using heart rate reserve as a better measure of relative workload. His work became foundational in exercise physiology and is still recommended by organizations like the American College of Sports Medicine (ACSM) for prescribing exercise intensity.

Practical Implications and Edge Cases

Why Resting Heart Rate Matters

Your resting heart rate is a key indicator of cardiovascular fitness. Athletes often have lower resting heart rates (40-60 bpm) while sedentary individuals may be above 80 bpm. The Karvonen formula adjusts for this: a fitter person will have a larger HRR and thus a lower target HR for the same intensity. This means two people of the same age could have very different target zones. For a deeper look into what target heart rate means, see What Is Target Heart Rate? Definition & Guide for 2026.

Age and Maximum Heart Rate

The estimated Max HR formulas (220 − age) are population averages and can vary significantly. It's best to use a measured Max HR from a stress test if available. The Karvonen formula is still valid with a measured Max HR. For women, the adjusted formula (226 − age) is often recommended because women tend to have slightly higher Max HR than men of the same age. Our Target Heart Rate for Women: Karvonen Formula Guide 2026 covers this in detail.

Edge Cases: Very Low or High Resting HR

If your resting heart rate is very low (e.g., 35 bpm for an elite athlete), the HRR becomes large, and the formula may yield target heart rates that seem low. That's normal — the athlete's heart is so efficient that it needs less effort for the same intensity. Conversely, a very high resting heart rate (e.g., 95 bpm) reduces the reserve, making the formula more sensitive to intensity changes. Always ensure your resting heart rate is measured accurately: after 5 minutes of quiet rest, first thing in the morning.

Importance of Intensity Percentages

The intensity percentage should match your fitness goal. For example, the American Heart Association recommends 50-70% for moderate exercise and 70-85% for vigorous activity. The Karvonen formula is most accurate between 40% and 90% of HRR; above 90% it may underestimate actual max effort. Use our Target Heart Rate Zone Chart: Understanding Intensities (2026) to see common zone breakdowns.

Calculating Your Zones Step by Step

To manually calculate your target heart rate using the Karvonen formula:

1. Estimate your Max HR (use 220 − age for men, 226 − age for women).
2. Measure your Resting HR (average of 3 mornings is best).
3. Calculate Heart Rate Reserve (Max HR − Resting HR).
4. Multiply HRR by desired intensity (as decimal).
5. Add Resting HR to that product.

Our step-by-step guide on How to Calculate Target Heart Rate Using Karvonen (2026) walks through examples and provides a printable table.

Summary

The Karvonen formula provides a more personalized target heart rate by accounting for your resting heart rate. It's the gold standard for setting exercise intensities and is used by athletes, coaches, and fitness professionals worldwide. Always remember that the numbers are guidelines — individual variations exist, and it's wise to combine heart rate monitoring with perceived exertion. For further questions, check the Target Heart Rate FAQ: Answers to Common Questions (2026).