How do you calculate BMI?

BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters (kg/m²). For imperial units, the formula is weight in pounds divided by height in inches squared, multiplied by 703.

What is a healthy BMI?

A healthy BMI range for adults is generally considered to be between 18.5 and 24.9.

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What is Body Mass Index (BMI)?

Body Mass Index (BMI) is a simple numerical measure of a person's weight in relation to their height. It is widely used by doctors and health professionals as a quick screening tool to identify possible weight problems for adults. While it does not measure body fat directly, research shows that BMI correlates closely with direct measures of body fat.

The BMI Formula (How to calculate it manually)

If you want to calculate your BMI without using a tool, you can use the standard mathematical formulas below:

Metric Units Formula

BMI = weight (kg) / [height (m)]²

Example: A person who weighs 70kg and is 1.75m tall has a BMI of 70 / (1.75 x 1.75) = 22.9

Imperial Units Formula

BMI = [weight (lbs) / height (inches)²] × 703

Example: A person who weighs 160lbs and is 5'9" (69 inches) tall has a BMI of [160 / (69 x 69)] x 703 = 23.6

BMI Categories and Ranges

The World Health Organization (WHO) classifies adult BMI into the following standard categories:

Underweight: Less than 18.5
Normal Weight: 18.5 – 24.9
Overweight: 25.0 – 29.9
Obese: 30.0 or higher

Limitations of BMI

While BMI is a useful, quick screening tool, it does have some limitations. Because it only accounts for height and weight, it cannot distinguish between fat mass and muscle mass. As a result, highly muscular athletes (like bodybuilders) may be classified as "overweight" or "obese" even if their body fat percentage is very low. Additionally, it does not account for age, gender, or bone density.