A common forumla you may see floating around is this:
(HRmax) is 220 – age = HRmax
HOWEVER: this is neither accurate nor scientific. Current studies indicate that no formula currently exists that is an accurate predictor of HRmax. however, the least objectionable formula is this:
HRmax = 205.8 − (0.685 × age)
Many heart rate measuring devices exist. Some people simply count their pulse rates.
Step 2: Calculate your resting heart rate (HRrest)
This is found by taking your pulse (or using your heart rate monitor) as soon as you wake up. The general standard is to do this for three consecutive mornings and calculate the average.
HRrest = resting heart rate day 1 + resting heart rate day 2 + resting heart rate day 3 / 3
Step 3: Calculate reserve heart rate (HRreserve)
To calculate your reserve heart rate, use this formula:
HRreserve = HRmax – HRrest
As your fitness improves, your resting heart rate will decrease thus increasing the reserve heart rate.
Step 4: Calculating your target heart rate
HRtarget= (HRreserve x % intensity) + HRrest
For example, if you want to target a 70% intensity, you would use:
HRtarget= (HRreserve x .7) + HRrest