Using the Mifflin-St Jeor equation based on weight, height, age, and gender.
Your TDEE = BMR × activity factor. This is your maintenance calories.
Subtract 500 cal/day to lose ~1 lb/week. A sustainable rate for most people.
One pound of body fat contains approximately 3,500 calories. A daily deficit of 500 calories creates a weekly deficit of 3,500 calories, resulting in about 1 pound of weight loss per week. This is considered a safe and sustainable rate by most health organizations.