Karvonen Formula Calculator

How to use the Karvonen Formula Calculator

What this calculator does

This calculator estimates a target exercise heart rate with the Karvonen, or heart-rate-reserve, method. It combines your resting heart rate, your maximum heart rate, and a chosen exercise intensity. The result is a beats-per-minute target that can help you compare a planned effort with a heart-rate reading during aerobic exercise. It is a mathematical training estimate, not a diagnosis, fitness clearance, or individualized medical prescription. Heart rate can be affected by medications, illness, temperature, hydration, stress, and measurement error, so a calculated target should be interpreted in context.

When to use it

• When planning an aerobic workout and you want a heart-rate target based on heart-rate reserve rather than a simple percentage of maximum heart rate.
• When comparing how the same resting and maximum heart rates translate into different training intensities, such as 50%, 70%, or 85% of reserve.
• When you know a measured maximum heart rate and want to use it directly instead of relying on an age-based estimate.
• When reviewing exercise data from a watch or chest strap and you want a consistent reference point for a chosen intensity.

How to calculate

The calculator opens with a complete demonstration: resting heart rate 60 bpm, age 30 years, and intensity 70%. In estimate mode, maximum heart rate is calculated as 220 – age, so the example uses 190 bpm. That produces a heart-rate reserve of 130 bpm and a target heart rate of 151 bpm. The example is calculated immediately, and its Excel workbook is ready to download on first open.

1. Replace Resting heart rate with your resting pulse in beats per minute.
2. Under Do you know your maximum HR?, keep No, estimate it to use age, or choose Yes, enter it to supply a known maximum directly.
3. If estimating, enter Age in years. If entering a known maximum, use the Maximum heart rate field instead.
4. Enter Intensity as a percentage from 0 to 100. Results update as you type.
5. Read Target heart rate, Maximum heart rate, and Heart-rate reserve, then use Download Excel if you want the current assumptions and results in an XLSX workbook.

Reset intentionally clears the demonstration and all semantic input data. After Reset, the calculator shows an empty state and Download Excel is disabled until a complete valid input set is entered again.

Input guide

Resting heart rate is required and accepts a plain whole or decimal number in bpm from 20 to 220. A realistic example is 60 bpm. A lower resting value increases heart-rate reserve when maximum heart rate stays fixed; a higher value reduces the reserve. Enter only the number, not letters or a pasted unit string. Resting heart rate must also remain below maximum heart rate for the Karvonen model to produce a positive reserve.

Do you know your maximum HR? is a required two-option control. Choose No, estimate it when you want the calculator to use the age equation, or Yes, enter it when you have a maximum value you intend to use directly. Switching modes changes which maximum-heart-rate input is required; it does not convert one measurement into another.

Age is required only in estimate mode. Enter a whole number from 1 to 120 years; 30 years is the startup example. The calculator applies maximum HR = 220 – age. Increasing age lowers the estimated maximum and usually lowers the target, all else equal. Do not enter a birth year or text such as “30 years.” The 220 – age relationship is an approximation, not a measured physiological limit.

Maximum heart rate is required only in direct-entry mode. Enter a plain numeric value from 40 to 260 bpm, such as 190. It must exceed resting heart rate. Raising this value increases reserve and usually raises the target at intensities above 0%. Use a value that is meaningful for your situation; do not enter a target heart rate in this field by mistake.

Intensity is required and accepts a percentage from 0 to 100; 70% is the startup example. Enter 70 for 70%, not 0.70. Higher intensity moves the target upward through the available heart-rate reserve; 0% returns the resting heart rate, while 100% returns the maximum heart rate. The American Heart Association provides broader context on target heart rates and exercise intensity, although its general percentage ranges are not identical to every heart-rate-reserve calculation.

Output guide

Target heart rate is the primary estimate in bpm. It is driven by resting heart rate, maximum heart rate, and intensity. At 0% it equals resting heart rate; at 100% it equals maximum heart rate. A higher target does not automatically mean a better or safer workout. Maximum heart rate is either the age-derived estimate or the directly entered value, shown in bpm. Heart-rate reserve is maximum heart rate minus resting heart rate, also in bpm; it represents the span that the Karvonen method scales by intensity. The four summary pills repeat the current Target HR, Heart-rate reserve, Maximum HR, and Intensity so the key assumptions and result remain scannable.

Worked example

With the startup values, resting heart rate is 60 bpm and age is 30, so estimated maximum heart rate is 220 – 30 = 190 bpm. Heart-rate reserve is 190 – 60 = 130 bpm. At 70% intensity, the reserve contribution is 130 × 0.70 = 91 bpm. Add the resting rate: 91 + 60 = 151 bpm. That is the exact first-open target shown by the calculator and written to the startup workbook.

Learn more

The original Karvonen research is indexed by the U.S. National Library of Medicine in the 1957 longitudinal heart-rate training study. For a non-numeric check on workout effort, the CDC also describes the talk test and other ways to gauge physical-activity intensity.