How Many Calories

Determining Your Body’s Daily Calorie Needs You probably understand that, just as we’re all different, we all require a different amount of calories each day for good health. To figure out how many calories any one individual requires, we need to gather some basic information and then do a little math. It’s not hard. And the good news is that understanding your body’s calorie requirements helps you make healthy decisions about what to eat.

There are two ways to calculate your energy needs. First we’ll show you the accurate method and then the easy method.


Calculate your BMR
To begin, you need to calculate your basal metabolic rate, or BMR. This refers to the amount of energy our bodies need to function. About 65 per cent of the calories we take in every day get used for basic functions such as respiration and maintaining body temperature. Things that influence BMR include weight, height, age and sex. For this step in the process, we’ll use a formula known as the Harris-Benedict formula.

For adult males:

66 + (6.3 x body weight in lbs.) + (12.9 x height in inches) – (6.8 x age in years) = targeted daily caloric intake

For adult females:

655 + (4.3 x body weight in lbs.) + (4.7 x height in inches) – (4.7 x age in years) = targeted daily caloric intake

Calculate energy expended through physical activity

This next step in the process takes into account the amount of energy you burn walking around, doing chores, exercising and so forth. In general, physical activity contributes 20-30 per cent of the body’s total energy expenditures. To calculate calories burned during physical activity, we multiply our BMR by the activity multiplier that most closely matches our physical activity habits:

Activity Multiplier

  • If you are sedentary (little or no exercise, desk job), multiply your BMR by 1.2
  • If you are lightly active (light exercise/sports 1-3 days a week), multiply your BMR by 1.375
  • If you are moderately active (moderate exercise/sports 3-5 days a week), multiply your BMR by 1.55
  • If you are very active (hard exercise/sports 6-7 days a week) multiply your BMR by 1.725

Total daily energy expenditure (TDEE)

Let’s look at the example of a person with a BMR of 1300 calories a day who is moderately active. To determine the individual’s total daily energy expenditure, or TDEE, multiply 1300 by 1.55.

1300 x 1.55 = 2015 calories per day

Thermic effect of food

The expression “thermic effect of food” is used to describe the energy your body uses to manage the food it takes in. The processes involved include chewing, swallowing, digesting and transporting. A key factor affecting the thermic effect is the kind of food we eat. Proteins are difficult to process; as much as 30 per cent of the energy released gets burned up during consumption. Fats go down extremely easily by comparison. The theremic effect is 2-3 per cent. Carbohydrates are in between.

Health experts estimate that, for people with a mixed diet, food management accounts for 10 per cent of total calories taken in. To calculate the thermic effect of food, multiply total calories consumed by 0.10.

Thermic effect of food = total calories consumed x 0.10

Combine the output from this calculation with the sum arrived at in calculating your TDEE and you’ll know the number of calories you require each day!


To get a rough idea of your daily calorie needs, use this formula.

  • If you’re sedentary, multiply your weight by 14
  • If you’re moderately active (3-4 aerobic sessions/week), multiply your weight x 17