Description The Karvonen formula is your heart rate reserve multiplied by the percentage of intensity plus your resting heart rate. For example, a 50-year-old with a resting heart rate of 65 would calculate as follows: 220 - 50 = 170 for HRmax. 170 - 65 = 105 for RHR. [105 x 0.75 (max intensity)] + 65 = about 144 bpm.
