The number of calories a woman should eat in a day varies based on her age, activity level, and health goals, but generally, adult women should consume between 1,600 and 2,400 calories daily according to the Dietary Guidelines for Americans 2020-2025. For example, a sedentary woman aged 21-25 might need about 2,000 calories per day, while an active woman of the same age might need about 2,400 calories. Calorie needs typically decrease with age and increase with activity level. Consuming fewer than 1,200 calories per day is not recommended as it may lead to nutrient deficiencies and health issues. The exact daily calorie intake can be personalized further considering factors like weight, height, and metabolism.