How many calories a day to weigh 160 pounds?

1 watt / hour per kilogram. 280lbs * 0.45359237 = 127.0059Kg For calorie burning, sleep burns less, so we use a 20 hr day to make the formula match reality. 127.0059Kg * 20hrs = 2540.117 Calories. To lose a pound it is accepted that you must burn 3500 calories (without replacing them, so eat 3500 calories less than you should to maintain your weight over a period of time and you will lose one pound).