Karvonen Heart Rate Formula
Calculate target heart rate for exercise using the Karvonen formula: THR = ((HRmax - HRrest) x intensity) + HRrest.
The Formula
The Karvonen formula, developed by Finnish physiologist Martti Karvonen in 1957, is one of the most accurate methods for calculating target heart rate during exercise. Unlike the simpler percentage-of-max method, the Karvonen formula accounts for your resting heart rate, which makes it more personalized and accurate.
The formula uses what is called the Heart Rate Reserve (HRR), which is the difference between your maximum heart rate and your resting heart rate. This reserve represents the range of heart rates your body actually uses during physical activity. By applying a percentage of this reserve and adding back the resting heart rate, the formula gives a target that is tailored to your individual fitness level.
To use the Karvonen formula, you first need to know your maximum heart rate. The most common estimate is HRmax = 220 - age, though more accurate formulas exist. You also need your resting heart rate, which is best measured first thing in the morning before getting out of bed. A typical resting heart rate for adults is between 60 and 100 beats per minute, while well-trained athletes may have resting rates as low as 40 to 50 bpm.
Exercise intensity zones typically range from 50% to 85% of heart rate reserve. Light exercise corresponds to 50-60%, moderate exercise to 60-70%, vigorous exercise to 70-80%, and high-intensity training to 80-90%. Training within specific zones helps target different fitness goals such as fat burning, cardiovascular endurance, or anaerobic threshold improvement.
The Karvonen method is particularly valuable because two people of the same age but different fitness levels will get different target heart rates, reflecting the fact that a fit person with a lower resting heart rate has a larger working range available.
Variables
| Symbol | Meaning |
|---|---|
| THR | Target Heart Rate (beats per minute, bpm) |
| HRmax | Maximum Heart Rate (bpm), estimated as 220 - age |
| HRrest | Resting Heart Rate (bpm), measured at rest |
| %Intensity | Desired exercise intensity (decimal, e.g. 0.70 for 70%) |
Example 1
A 30-year-old with a resting heart rate of 65 bpm wants to exercise at 70% intensity. What is their target heart rate?
HRmax = 220 - 30 = 190 bpm
Heart Rate Reserve = 190 - 65 = 125 bpm
THR = (125 × 0.70) + 65
THR = 87.5 + 65
Target Heart Rate = 152.5 bpm (approximately 153 bpm)
Example 2
A 50-year-old athlete with a resting heart rate of 48 bpm wants their target zone for moderate exercise (60-70%). What range should they aim for?
HRmax = 220 - 50 = 170 bpm
Heart Rate Reserve = 170 - 48 = 122 bpm
Lower bound: (122 × 0.60) + 48 = 73.2 + 48 = 121 bpm
Upper bound: (122 × 0.70) + 48 = 85.4 + 48 = 133 bpm
Target zone: 121 to 133 bpm
When to Use It
Use the Karvonen formula when you need to:
- Set personalized heart rate targets for cardio workouts
- Design training programs with specific intensity zones
- Monitor exercise intensity during running, cycling, or swimming
- Compare fitness progress over time as resting heart rate changes
- Prescribe safe exercise intensity for cardiac rehabilitation patients
The Karvonen method is preferred over the simpler percentage-of-max method because it accounts for individual fitness levels through the resting heart rate component.