BMI Explained: Formula, Categories and Limits

How BMI is calculated

BMI is weight divided by height squared. In US units: BMI = 703 × weight(lb) ÷ height(in)². It gives a single number to screen weight status.

Categories (WHO/CDC)

Underweight below 18.5, normal 18.5–24.9, overweight 25–29.9, and obese 30 or above.

What BMI misses

BMI does not distinguish muscle from fat or where fat is stored. Very muscular people can read high. Use it as a general reference alongside waist size and body fat.

FAQ

Is a normal BMI always healthy?

Not necessarily. Someone with normal BMI but high body fat may still have health risks. Consider other measures too.

Does BMI differ for athletes?

Yes. Muscle weighs more than fat, so athletes often have a high BMI without excess fat.

Related calculators

• BMI Calculator
• Calorie (TDEE) Calculator