Grams to Calories Calculator

Every calorie on a nutrition label comes from just four things: protein, carbohydrate, fat, and sometimes alcohol. Each delivers a fixed amount of energy per gram, and those numbers are the Atwater factors. Protein and carbohydrate give about 4 calories per gram. Fat is the dense one at 9 calories per gram, more than double the others, which is why a spoonful of oil carries so much energy. Alcohol sits at 7.

So converting grams to calories is just multiply and add. Twenty grams of protein is 80 calories, 30 grams of carbs is 120, and 10 grams of fat is 90, for 290 calories total. This calculator does that for whatever macros you enter and then shows what fraction of the total each one contributes, which is the part most people actually care about when they read a label or plan a meal.

One honest caveat. The number you get may not match the manufacturer’s stated calories to the last digit. Labels are allowed to round, and they often use a lower factor for fiber, which is a carbohydrate your body cannot fully digest. Fiber yields closer to 2 calories per gram than 4, so a high-fiber food will read a little high here. For a candy bar or a steak the match is close. For a bowl of beans, treat the carbohydrate figure as total carbs and expect the real count to come in somewhat lower.

Enter the grams of each macro from a label or a recipe. Leave any field blank if it does not apply.