To find out how much you weigh, you simply step on a scale. But your weight alone can't tell you whether you're underweight, healthy, or overweight. If you're 6'4" and you weigh 200 pounds, you're probably at a healthy weight; but if you're 5'9" and weigh 200 pounds, you're probably overweight.

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Because both height and weight are important to help determine if someone is overweight, scientists came up with a mathematical formula called Body Mass Index (BMI). This simple measurement helps doctors determine whether their patients are at a healthy weight or need to lose or gain a few pounds.

In this article, you'll learn how the BMI is calculated and what the numbers mean to your health.