Daily Calorie Needs calculator  determine your daily calorie needs to maintain weight using Harris Benedict equation to calculate your BMR  Basal Metabolic Rate.
Bascal Metabolic Rate

For people with healthy weight this equation is quiet accurate, the only factor that is omitted by the Harris Benedict Equation is Lean Body Mass.
Therefore, note that leaner bodies need to consume more calories (underestimate calorie needs) and obese bodies need to consume less calories (overestimate calorie needs).
Daily Calorie Needs is an approximation of your total amount of daily kilocalories you would burn that corresponds to yours daily activity level in order to maintain a certain weight.
This calculator uses the Harris Benedict Equation to calculate your Basal Metabolic Rate and then apply an activity factor.
BMR  Basal Metabolic Rate is the amount of calories you would burn if you were asleep all day.