BMI Calculator: Find Your Weight Category

How the BMI Calculator Works

This calculator turns your height and weight into a Body Mass Index (BMI) score, then places that score in one of four weight categories: underweight, normal weight, overweight, or obese. Enter height and weight in metric units (centimeters and kilograms) or switch to US units (feet, inches, and pounds), and the result appears with a marker on a color-coded scale running from 15 to over 40, matching the categories below.

The Formula

BMI is calculated by dividing weight in kilograms by height in meters squared. When you enter feet, inches, and pounds, the calculator first converts feet and inches to meters using 0.0254 meters per inch, and pounds to kilograms using 0.453592 kilograms per pound, then applies the same formula, so the result matches what a metric calculation would give for the same body.

BMI = weight (kg) / height (m)²

Worked Example

Someone who is 5 feet 9 inches tall (69 inches, 1.753 m) and weighs 160 lbs (72.57 kg) gets a BMI of 23.6: dividing 72.57 by 1.753 squared, or 3.073, equals 23.6, which sits inside the normal weight range of 18.5 to 24.9. A second person, 160 cm (1.60 m) and 50 kg, gets 50 divided by 1.60 squared (2.56), or 19.5, also in the normal range.

BMI Categories

The categories below follow the World Health Organization's classification for adults, which applies to men and women without adjusting for age.

These ranges are a screening reference, not a diagnosis. BMI does not measure body fat or muscle mass directly, and factors such as bone structure and overall body composition affect how the number reflects health risk, so a doctor or dietitian should confirm any concern before you act on the result.