How to Calculate Calories in Food

Updated March 23, 2017

Through a variety of available resources and messages, people -- whether they’re health-conscious or not -- know that sugar-laden foods such as sweets and ice cream are “unhealthy” and that fruits and vegetables are generally low in calories. A calorie is a unit of energy expenditure and a way of measuring the energy that food provides to your body. Calories provide energy, protein, carbohydrates, fat and nutrients. Your body turns food into fuel by burning it to produce calories. Counting and keeping track of calories is not difficult, but you should know about different food group calories and be aware of some calorie myths.

Read food-container labels. The Food Standards Agency (FSA) and its American counterparts -- the U.S. Food and Drug Administration and the U.S. Department of Agriculture -- require nutrition information, including calorie content, on nearly all packaged foods. Information for non-packaged food items, such as fruits and vegetables or non-packaged meat, is normally displayed near the products.

Research elsewhere if you can’t decipher the information contained on labels. There’s plenty of help available at libraries, bookstores and especially online. The calorie information on a food label, for example, is the amount of calories contained in one serving. This distinction can be overlooked, especially on an item like a 140g (5 oz) can of tuna. This seemingly small amount of tuna, which many people might assume constitutes a single serving, actually is considered 2.5 servings on most tuna-can labels as of 2010.

Learn how to translate food-label information not directly identified as “calories.” It’s important to know, for instance, how many calories are derived from fat and carbohydrates, which are listed by weight in grams and as percentages per serving on the label. There are nine calories per gram of fat and four calories per gram in carbohydrates and protein. A rule-of-thumb recommendation is a 45/35/20 percentage split from calories derived from carbohydrates, fat and protein. This ratio will differ depending on your body type, weight, age and level of physical activity. That 140g can of tuna contains nearly half the recommended daily allowance (RDA) for fat and about 25 percent of your carbohydrate needs, so you’ll have to monitor your diet the rest of the day to ensure you don’t get too many calories from fat and carbs.

Read carefully the calorie information on products labelled as “fat free” or “low fat.” These items must meet specific fat-content requirements, but the amount of calories in such products can be extremely high.

Use a calorie calculator, especially as you learn the calorie content of different foods. You can purchase hand-held calculators for in-store use or use online versions.


Generally, 3,500 calories equals 454g (1 lb) of fat. You need to burn 3,500 calories more you than consume to lose 454g of weight. Cutting 500 calories from your daily diet, you'll lose about 454g per week.

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About the Author

John Kibilko has been writing professionally since 1979. He landed his first professional job with "The Dearborn Press" while still in college. He has since worked as a journalist for several Wayne County newspapers and in corporate communications. He has covered politics, health care, automotive news and police and sports beats. Kibilko earned a Bachelor of Arts in journalism from Wayne State University.