wikiHow Fat Calorie Calculator To calculate the number of calories from fat in a food, you need to know the total number of calories in the food and the percentage of calories that come from fat. Here's how to calculate fat calories: 1. Look at the nutrition facts label on the food package to find the total number of calories per serving. 2. Look for the total fat content on the label, and calculate the percentage of calories that come from fat by dividing the number of calories from fat by the total number of calories per serving. For example, if a food has 10 grams of fat and 100 calories per serving, the percentage of calories from fat is 10/100 = 0.1, or 10%. 3. Multiply the total number of calories per serving by the percentage of calories that come from fat to calculate the number of calories from fat. For example, if a food has 200 calories per serving and 30% of the calories come from fat, the number of calories from fat is 200 x 0.3 = 60. In summary, to calculate the number of calories from fat, multiply the total number of calories per serving by the percentage of calories that come from fat. Example: Let's say you have a food item that has the following nutrition facts label: Serving size: 1 bar (45g) Calories per serving: 200 Total fat: 10g Saturated fat: 4g To calculate the number of calories from fat in this food item, follow these steps: Look at the total number of calories per serving, which is 200. Look at the total fat content, which is 10g. Calculate the percentage of calories that come from fat by dividing the number of calories from fat by the total number of calories per serving. Fat provides 9 calories per gram, so we can multiply the total fat content by 9 to get the number of calories from fat: 10g of fat x 9 calories per gram = 90 calories from fat Then we can divide the number of calories from fat by the total number of calories per serving to get the percentage of calories that come from fat: 90 calories from fat / 200 total calories per serving = 0.45, or 45% So, 45% of the total calories in this food item come from fat. To calculate the number of calories from fat, we can multiply the total number of calories per serving by the percentage of calories that come from fat: 200 total calories per serving x 0.45 = 90 calories from fat Therefore, this food item contains 90 calories from fat. Page