Even if you don't have a scale at home, take the weight of the package and divide it by the number of servings you plan to get out of it. Example: take 1/2 pound (8 oz) of turkey breast and split it into two 4 oz. portions. Like Jay said, then you figure calories by the ounce. I know that Boar's Head turkey breast is 30 calories per ounce, so a 4 oz portion = 120 calories.