When it comes to calories and fat in foods, all those numbers can appear overwhelming at first. However, calculating calories from fat is a very straight forward process. You just need to know how many fat grams are in the food and you can easily do the conversion. These are the steps you can follow to complete the calculation yourself.
Find the label for the food product. If you are eating a fresh food or it does not have a label, use a nutritional database such as the U.S. Department of Agriculture National Nutrient Database for Standard Reference to seek out your food and related nutritional information.
Determine the number of total fat grams in the product. On a standard food label, this is the first thing listed after the calories.
Multiply the grams of total fat by nine because there are nine calories in one gram of fat. For example if the label says the food has five grams of total fat, five times nine equals 45.
Locate the number of servings if analyzing a packaged food. For example, at the top of the label it will say what a serving is; this could be in ounces, cups or tablespoons. Then in parentheses it often says how many servings the whole package contains. Multiply the calories from fat by the number of servings in the package to get the total calories from fat.