Maximum Heart Rate
Maximum Heart Rate (MHR) starts out at 220 beats per minute.
And falls by one beat each year.
Therefore, you can calculate your Maximum Heart Rate by deducting your age from 220.
So a good estimate of Maximum Heart Rate for a 60 year old is 160 (220-60 (age))
and for a 20 year old is 200 (220-20).
A  approximation is to accept the one year one beat rule until you reach 30.
Maximum Heart Rate falls by less than one beat each year.
After 30 it is only .5 a beat per year.
This may be summarized by the following formula:

Maximum Heart Rate equals:

(Age 30 or below)

220 - age


(Age above 30)

190 - (age-30)/2
 Determine your resting heart rate
Your resting heart rate is determined by counting your pulse
(at your wrist or the side of your neck) for a full 60 seconds.
The better your level of cardiovascular fitness, the lower
your resting heart rate will be. The average resting heart rate is 72 beats per minute(bpm).
If your heart rate is substantially higher than the average (80-90 bpm)
 it may be a sign of poor cardiovascular fitness.
A resting heart rate higher than usual can also be a sign of overtraining.
Low resting heart rates are usually an indicator of excellent cardiovascular fitness.
Determine your estimated maximum heart rate (EMHR)
The formula for estimated maximum heart rate is 220 - your age
Example:
you are 30
220 - 30 = 190
your EMHR is 190 beats per minute

Determine your heart rate reserve (HRR) by subtracting your RHR from your

EMHR
Example:
your RHR is 58 bpm
your MHR is 190
190 - 58 = 132
your HRR is 132 bpm

 Multiply your HRR by your desired intensity range

example
you are a beginner
select the moderate intensity range of 60-65%
multiply your HRR by 60-65%
132 X .60% = 79
132 X .65% = 86
Step 6: Add your RHR to your HRR to determine your target heart rate
79 (HRR) + 58 (RHR) = 137 (THR at 60%)
86 (HRR)+ 58 (RHR) = 144 (THR at 65%)
Your target zone is 137 - 144 beats per minute
The Age-Predicted Method

This is the simplest method of determining your target heart rate and this should
be used if you don’t know your resting heart rate.
Step 1: determine your estimated maximum heart rate (MHR)
The formula for maximum heart rate is 220 - your age
Example:
you are 30
220 - 30 = 190
your EMHR is 190 beats per minute
Step 2: Select an intensity range to work in based on your goals and on your personal
fitness level. The target zone for the age-predicted method is 70-85% of your estimated
maximum heart rate
10-second pulse counts.
Simply divide your target heart rate in beats per minute by 6 to find your 10 second count:

Example:
Your target heart zone is 133 - 143
Divide 133 by 6 to for your low end of range 10-second count: = 22
Divide 142 by 6 to for your high end of range 10-second count: = 24


find your target heart-rate zone by calculating 50 percent and 85 percent of your maximum. Here’s the math for a 40-year-old man:

220 – 40 = 180

This is his estimated maximum heart rate.

180 x 0.50 = 90

This is the low end of his target zone. If his heart beats less than 90 times per minute, he knows that he’s not pushing hard enough.

180 x 0.85 = 153