A BMI (Body Mass Index) calculator is a handy tool used to gauge an individual's body fat based on their height and weight. It's a straightforward calculation that provides a numerical value indicating whether a person's weight aligns with their height in a healthy manner. By dividing a person's weight in kilograms by their height in meters squared, the BMI value obtained can be easily interpreted using standard categories like underweight, normal weight, overweight, or obese.