Are you curious about how many calories in a chicken breast? This chicken cut is very versatile and contains low fat and plenty of protein. A 3.5-ounce serving contains 165 calories, 31 grams of protein, and 3.6 grams of fat. Eighty percent of the calories in a chicken breast come from protein, and only twenty percent comes from fat. However, depending on the way you cook your chicken breast, its fat content may increase by 20 percent.