BMI Explained: What Body Mass Index Can and Can't Tell You

Body Mass Index (BMI) is a simple screening number that relates your weight to your height. It is widely used because it is quick to calculate and easy to compare.

The BMI formula

BMI = weight (kg) / height (m)²

For example, a person weighing 70 kg and 1.75 m tall has a BMI of 70 / (1.75 × 1.75) = 22.9.

Standard categories (adults)

• Below 18.5 — underweight
• 18.5 to 24.9 — normal range
• 25.0 to 29.9 — overweight
• 30.0 and above — obese

Important limitations

BMI does not distinguish muscle from fat, or account for age, sex, ethnicity and body composition. Athletes can have a high BMI with low body fat. It is a general screening tool, not a diagnosis.

Check your BMI

Use our free BMI Calculator for an instant result in metric or imperial units.

This is educational information, not medical advice. Consult a qualified healthcare professional for guidance about your health.