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How to Count and Calculate Calories

What Are Calories?

A Calorie is a unit of energy that measures how much energy food provides to the body. The body needs calories to function properly. The amount of Calories in food gives you energy, protein, carbohydrate, nutrients and fat to fuel your body. When you eat food, your body turns the food into fuel, burning it to produce calories (energy).

The calories in your food come from sources such as carbohydrates, proteins, and fats. For example, a gram of carbohydrate contains 4 calories. A gram of protein also contains 4 calories, where as a gram of fat contains 9 calories, which is more than twice the amount of carbohydrates and protein. This is why a food with the same size serving may have far more calories. Nutritionists do not recommend calorie counting for teens unless a doctor has recommended it.

Kilojoules and calories calculations:

We normally refer to kilocalories as Calories, so when you see 800 calories on a food label it actually means 800 kilocalories, and the same applies when you calculate an activity that burns 800 calories. When referring to food consumption and energy expenditure we refer to them in multiples of 1,000. Thus 1,000 calories = 1 kilocalorie or kcal.

A calorie is the amount of energy (or heat) needed to increase the temperature of one gram of water by 1C. So 1000 calories = 1 kilocalorie, is the energy it takes to raise the temperature of 1kg of water by 1 degree Celsius.

There are 239 calories in 1 kilojoule - A joule is a 1 unit of electrical energy it takes to equal the current of 1 ampere passed through a resistance of 1 ohm for one second. 1,000 joules = 1 kilojoules or kJ.

One calorie has the same energy value as 4.186 kilojoules. It takes 3,500 calories to equal one pound of body weight.

1 calorie = 4.2 joules so 1 kilocalorie = 4.2 kilojoules.

The energy value per GRAM of various food components includes:

  • Water = 0kJ (0 Cal)
  • Protein = 17kJ (4 Cal)
  • Dietary fibre = 13kJ (3 Cal)
  • Fat = 37kJ (9 Cal)
  • Alcohol = 29kJ (7 Cal)
  • Carbohydrates = 16kJ (4 Cal)
Calories You Burn During the Following Activities

Duration of Activity: Minutes
Your Weight in lbs.


Calories Burned =
Daily Protein and Calorie Needs
Your Current Weight: lbs.

 Calories a day to lose weight
 To maintain weight
 Grams of protein needed a day
Calorie Requirements a Day for Women
AgeSedentaryLow ActivityActive
2-3 yrs110012501400
4-5 yrs120013501500
6-7 yrs130015001700
8-9 yrs140016001850
10-11 yrs150018002050
12-13 yrs170020002250
14-16 yrs175021002350
17-18 yrs175021002400
19-30 yrs190021002350
31-50 yrs180020002250
51-70 yrs165018502100
71 yrs +155017502000
Calorie Requirements a Day for Men
AgeSedentaryLow ActivityActive
2-3 yrs110013501500
4-5 yrs125014501650
6-7 yrs140016001800
8-9 yrs150017502000
10-11 yrs170020002300
12-13 yrs190022502600
14-16 yrs230027003100
17-18 yrs245029003300
19-30 yrs250027003000
31-50 yrs235026002900
51-70 yrs215023502650
71 yrs +200022002500
  • Sedentary: Your typical daily routine requires little physical movement (e.g., sitting for long periods, using a computer, relying primarily on motorized transportation) and you accumulate little physical activity in your leisure time.
  • Low Activity: Your typical daily routine involves some physical activity (e.g., walking to bus, mowing the lawn, shovelling snow) and you accumulate some additional physical activity in your leisure time.
  • Active: Your typical daily tasks involve some physical activity and you accumulate at least 2 1/2 hours of moderate- to vigorous-intensity aerobic physical activity each week. Moderate to vigorous physical activity will make you breathe harder and your heart beat faster.

Also see Basal Metabolic Rate Calculator - Calories Burned when Resting

How many calories should you need a day?

If you're at a desirable body weight and have plenty of energy, your calories in food intake is probaly ok. However if you're gaining weight and feel tired a lot of the time, you may want to consider counting your intake of calories in food and changing your daily diet, because as you ingest extra calories your body will convert the excess energy to body fat. Ensure you don't eat less than 1200 calories a day, that's the minimum you need to get your nutrients and stay healthy.

The USDA figures show the average male 5 feet 10 inches in height and weighing 174 pounds, needs 2,900 calories per day - performing light to moderate activity. The average female, 5 feet 4 inches and weighing 138 pounds, needs 2,200 calories per day.

For healthy eating see our New Food Pyramid

What is your desirable weight?

Being overweight or underweight is defined in terms of weight for height, according to the Body Mass Index (BMI).

To calculate your BMI see our Body Mass Index Calculator

To find your height to weight ratio see our Height to Weight Ratio Chart

Some tips to help lose weight:

a) Start everyday with breakfast because your body will absorb as many nutrients as possible from the breakfast and this will boost your body metabolism.

b) Instead of one big meal, try to eat more times having smaller meals and calculate your calorie intake. You don't get fat because of a lack of exercise, you get fat because you don't eat the right foods at the right intervals each day.

c) Eat slowly, chew more and drink more water with the meal.

d) Choose foods that are low in fat and high in complex carbohydrates, such as whole-grain cereals and breads.

e) Drink lots of water, a glass every one - two hours will keep you feeling full.

f) Try a different type of food each day. The new flavors will save you from diet boredom.

g) Change your diet from high calorie foods, eg. fatty meats, oily dressings, regular soft drinks to lower-calorie options like fish, zero-calorie dressings and water.

h) Switch to high fiber foods, low fat diet and, most importantly, exercise regularly.


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