Your active metabolic rate is the amount of calories that your body burns in a single day. This is an important piece of information to have for anyone who is trying to lose weight, or gain weight. Calculating it takes some math, but you only have to do it once!
Things You'll Need
 A calculator
 Your weight, height, age, and gender

First, write down your weight in pounds, your height in inches, and your age in years.

Before we get your Active Metabolic Rate (AMR), we are going need your Basal Metabolic Rate (BMR). Your BMR is the amount of calories burn just to stay alive. You would still burn this amount even if you slept 24 hours a day.

Now, use the following formula to calculate your BMR.
Adult Women:
655 + (4.3 x weight in pounds) + (4.7 x height in inches)  (4.7 x age in years)Adult Men:
66 + (6.3 x weight in pounds) + (12.9 x height in inches)  (6.8 x age in years) 
Will also need an estimate of how active you are. This is called an Activity Modifier.
Pick an activity modifier that estimates how much exercise you receive, in general.Your activity modifier is:
1.25 if you are lightly active.
1.40 if you exercise almost every day.
1.60 if you are a full time construction worker, or professional athlete. 
Now we have all the information we need to calculate your Active Metabolic Rate.
Just multiply your previous two answers together.
The formula is:
(BMR) x (Activity Modifier) = Active Metabolic Rate 
Now you know how many calories you burn each day! The beauty of having this information is that it puts you more in control of your metabolism. If you eat less than what you burn, you lose weight. If you eat more than what you burn, you gain weight. Great work!
Tips & Warnings
 Consult your doctor before embarking upon any weightloss or dietary plan.