Calorie calculators are not meant to give you your exact daily calorie expenditure, we're not robots. They are only estimates. Only tracking your weight loss for a few weeks will you get an accurate picture of your maintenance calories. When I started the calculator said my maintenance was 1,800 calories. After tracking my weight loss for a few weeks (and being very anal with daily food calorie calculations) I realized my maintenance was closer to 1,900-2,000 calories. That doesn't mean I throw out the use of calorie calculators. It was a great starting point. Without it I wouldn't know to start my maintenance calories at 1500 or 2000 or 2300 etc.