How Many Calories Do I Need?

How many calories should I consume in order to lose weight? What if I want to gain weight? You may have asked yourself these questions more than once. Luckily, there's an equation that can help guide you. The Mifflin-St Jeor method, the most recently constructed caloric-need formula, approximates the number of calories we need in order to lose, gain, or maintain weight.

Male BMR = 10 × weight (kg) + 6.25 × height (cm) – 5 × age + 5
Female BMR = 10 × weight (kg) + 6.25 × height (cm) – 5 × age – 161

* lb. / 2.2 = kg.
* in. x 2.54 = cm.

For example: John, 40 years old, weighs 95 kg. (209 lb. / 2.2), and has a height of 182.88 cm. (72 in. x 2.54). His BMR (Basal Metabolic Rate) -- the number of calories you would burn if you did nothing all day -- is 1,898. (950 + 1,143 - 200 + 5)

10 x 95 = 950
6.25 x 182.88 = 1,143

Now we need to adjust this number to account for activity. How do we do that? We multiply BMR by an approximate activity factor. The numbers are:
1.200 = sedentary (little or no exercise)
1.375 = light activity (light exercise / 1-3 days per week)
1.550 = moderate activity (moderate activity / 3-5 days per week)
1.725 = very active (hard exercise / 6-7 days per week)
1.900 = extra active (very hard exercise / every day and physical job)

John works out 6 times per week, and thus, is considered to be very active. 

1,898 x 1.750 = 3,321.5

Therefore, according to Mifflin-St Jeor's formula, John needs to consume just over 3,321 calories per day to maintain his current weight. If John wants to lose approximately 1 lb. per week, he must restrict 3,500 calories a week (there are 3,500 in 1 lb. of weight); therefore, a good strategy would be to consume roughly 500 fewer calories per day (500 calories per day x 7 days per week). He would have to do the opposite to gain approximately 1 lb. per week. 

It should be noted, the formula is not perfect, as every person is different due to metabolic demands. 

Of course, if time is limited, you can always Google "caloric needs calculator".