BMR and TDEE
Your basal metabolic rate (BMR) is the energy your body uses at complete rest. This calculator uses the Mifflin-St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, plus 5 for men or minus 161 for women. Multiplying BMR by an activity factor from 1.2 to 1.9 gives your total daily energy expenditure (TDEE), the calories that keep your weight about the same.
Losing or gaining weight
A pound of body fat holds roughly 3,500 kcal (about 7,700 kcal per kg), so eating about 500 kcal a day below your TDEE loses about 1 lb a week. Slower changes are easier to keep up. If the target falls below 1,200 kcal (women) or 1,500 kcal (men), the calculator flags it, as very low intakes are best done with professional support.
About the macro split
The suggestion gives about 1.6 g of protein per kg of body weight, 25% of calories from fat and the rest from carbohydrates. It is a starting point: adjust to your preferences and see how your weight and energy respond over a few weeks.
Is anything sent to a server?
No. Everything runs in your browser. Nothing you enter is uploaded; settings you change are only remembered on this device.