Women between the ages of 31 and 50 generally require around 1,800 calories per day, according to the U.S. Department of Agriculture. However, individual calorie needs vary based on the activity level of a person, so a woman who is very physically active could need more calories each day.
The U.S. Department of Agriculture's website ChooseMyPlate.gov recommends an allowance of 1,800 calories per day for a 42-year-old woman who does less than 30 minutes of moderate physical activity each day. Of these calories, no more than 160 should be empty calories. Empty calories are solid fats and added sugars, which are found in foods such as cakes, cookies, sodas, sausages, bacon and pizza.