Calorie needs differ among individuals, and the exact number you need to maintain your weight depends on your age, activity level and body composition. Although only medical testing can precisely determine your daily calorie expenditure, you can get a workable estimate with a quick activity assessment. By eating more calories than you burn, you'll gain weight; by eating fewer calories, you'll shed pounds. To maintain your weight, balance the calories you burn with the calories you consume.
With a sedentary lifestyle that includes no physical activity beyond everyday tasks like walking through a parking lot, a 150-pound woman burns about 2,045 calories per day. With light activity -- the equivalent of walking casually two miles per day -- she burns 2,386 calories. With a moderately active lifestyle than involves brisk walking, yoga, dancing or other moderate cardio three to five times per week, she burns 2,523 calories per day. And with a heavy activity load that includes vigorous exercise such as running or playing team sports most days of the week, she burns 3,000 calories per day. Competitive endurance athletes may burn as many as 3,477 calories per day.