The TDEE (Total Daily Energy Expenditure) Calculator estimates the total number of calories your body burns each day, including both resting metabolism and physical activity. It first calculates your Basal Metabolic Rate (BMR) using the Mifflin–St Jeor equation and then multiplies it by an activity factor that represents your daily activity level. By entering your age, gender, height, weight, and activity level, you can determine how many calories you need to maintain your current weight. This helps create personalized diet and fitness plans—adjusting calories for weight loss, maintenance, or muscle gain with accuracy.