First calculate your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, then multiply by an activity factor. BMR for men: 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 5.

BMR (Basal Metabolic Rate) is the number of calories your body burns at rest to maintain basic functions like breathing, circulation, and cell production.

It depends on age, gender, weight, height, and activity level. Average needs are about 2000–2500 kcal/day for women and 2500–3000 kcal/day for men. For weight loss: eat 500 kcal less than your expenditure.