Fact Checked

How Are Calories per Serving Found?

Erin J. Hill
Erin J. Hill

In most cases, calories per serving are determined by figuring out how many grams of carbohydrates and proteins are found in certain foods and then multiplying by the number of calories found in those substances. This is not the most meticulous method, but it is fairly accurate and less time-consuming than previously used methods. Another method formerly used in determining the number of calories per serving a food involved placing a portion of the food in a container and then placing the container in water. The food was then burned and the temperature of the water was monitored. For each degree Celsius (33.8 degrees Fahrenheit)the water rose, one calorie was listed as being contained in the food.

Calories are a way of measuring the amount of energy within food. They are needed to fuel the body in all aspects of function. Those who eat too many or too few calories can suffer serious health problems. High calorie intake is related to obesity, which can lead to diabetes, heart disease, and many other health conditions. Low calorie intake can also cause problems because they body can't get the nutrients and energy it needs. Eventually organs begin to shut down if caloric intake dips too low. For this reason, it is important for many people to keep track of the calories per serving of foods being eaten.


Both carbohydrates and proteins have a specific number of calories per gram of weight. When determining the total number of calories per serving of a certain food, experts calculate how many proteins and carbs are present in grams, and then multiply that by the number of calories typically found in a gram of those substances. This is not always exact since not all carbohydrates can be calculated the same. For instance, grains and other carbs with insoluble fiber should not be calculated in the same way as those without.

Consumers can usually find the calories per serving of a particular food on the packaging, but this may not be true for all countries. It's also possible to calculate the number of calories by looking up the calories found in each ingredient contains in a particular packaged food. For instance, if one wanted to determine the calories per serving of meatloaf it would be necessary to add the calories of the eggs, meat, breading, and any other ingredients added. Calories in packaged foods can also be determined by contacting the food manufacturer.

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Discussion Comments


Anyone who is trying to lose weight needs to pay careful attention to the real serving size. Sometimes things which you would expect to be just one serving are actually two or three or four. You may look at the calorie content and think you are only eating 200 calories when in reality you are eating 600.

This is one way that food companies try to trick consumers into consuming more than they realize. The food companies establish the serving size. Oftentimes this is intentionally out of step with the portions that are offered. That 20oz bottle of soda may actually be 2 or 3 servings.


It's good to know how many calories you are eating but you don't want to get too hung up on it. I have a few friends that are obsessed with their weight and they count calories obsessively. It think it takes all the pleasure out of eating. It makes it seem like a transaction rather than something to be enjoyed and appreciated. Say what you will about their weight, I think that is unhealthy.


If you are eating prepared food it is pretty easy to find out the calories per serving. Just look on the side of the box. It is federal law that mass produced food products must contain easily readable nutrition information.

But if you are cooking food from scratch it can be harder to tell. You may be able to find the information online though. Lots of recipes that are feature both online and in cook books include detailed nutrition information.

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