BMI (Body Mass Index) is a calculation used to assess whether an individual has a healthy body weight relative to their height. It is calculated by dividing a person's weight in kilograms by the square of their height in meters (BMI = kg/m²). A BMI between 18.5 and 24.9 is generally considered normal, while values outside this range may indicate underweight, overweight, or obesity. Although BMI is a useful screening tool, it may not account for variations in muscle mass, distribution of fat, or other individual factors.