Find your maintenance calories, then the calories and macros to hit your goal.
Your Total Daily Energy Expenditure is the number of calories you burn in a day. It starts with your Basal Metabolic Rate (the energy your body uses at complete rest to keep you alive) and multiplies it by an activity factor for how much you move. TDEE is the figure that matters for weight goals, because weight change comes down to calories in versus calories out.
Turning it into a goal. To maintain weight, eat around your TDEE. To lose weight, eat below it: a deficit of roughly 500 calories a day tends to lose about half a kilo (a pound) a week, which is a sustainable pace. To gain muscle, eat a modest surplus above your TDEE alongside resistance training. Extreme deficits backfire by costing you muscle and slowing your metabolism.
It is an estimate, so adjust. Formulas give a starting point, but real metabolism varies. Track your weight over two to three weeks: if it is not moving the way you expect, adjust your intake by 100–200 calories and reassess. The calculator above gives your maintenance figure and targets for cutting and bulking.