Calories in Chicken Breast. Depending on the source, a 4-ounce single serving of skinless, boneless chicken breast contains between 110 and 184 calories. That’s a big range. But you can’t always trust calorie counts posted by manufacturers, as they may be off by as much as 20%. The size of your chicken breast will also affect the calorie count. A single serving of chicken breast is about four ounces or the size of the palm of your hand. Many commercially packaged chicken breasts are much larger than that, so if you eat a single breast, you’re probably eating more than a single serving.