Question: how many calories do you have to eat to gain a kilo?
Answer: Generally speaking, every 1kg of weight gain needs about 7000 additional calories [or 29 300 kilojoules]. So to gain 1kg in a week, you would need to eat your Daily Energy Expenditure (DEE) (calculated on the How Much Should I Be Eating Handout) plus a further 1000 calories [or 4 190 kilojoules] every day.