Work out the daily calorie deficit needed to reach your goal weight in a chosen number of weeks, with a safety check.
A calorie deficit means eating fewer calories than your body burns, so it draws on stored fat for energy and you lose weight. The size of the deficit sets how fast you lose.
Commonly 500 kcal a day for about 0.5 kg a week, or up to roughly 1,000 a day for faster loss. Bigger deficits are harder to stick to and risk muscle loss, so a moderate, sustainable deficit usually wins.
It is a useful approximation (about 3,500 kcal per pound). Real results vary with water, muscle and how your metabolism adapts, so use it to plan and adjust based on what the scale actually does over a few weeks.