SuperCalc

BMI Categories Explained

The World Health Organization defines six BMI categories: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), Obese Class I (30–34.9), Obese Class II (35–39.9), and Obese Class III (40+). Each category carries different health risk profiles. Use the calculator below to find your category, then review the reference table for a complete breakdown.

BMI Calculator

Enter your height and weight to calculate your Body Mass Index.

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BMI Categories

WHO classification of Body Mass Index ranges.

CategoryBMI Range
Underweight
< 18.5
Normal
18.5 – 24.9
Overweight
25 – 29.9
Obese I
30 – 34.9
Obese II
35 – 39.9
Obese III
40+

Frequently Asked Questions

What are the six BMI categories?
Underweight (<18.5): risk of malnutrition, osteoporosis. Normal (18.5–24.9): lowest health risk. Overweight (25–29.9): moderate increased risk. Obese I (30–34.9): high risk. Obese II (35–39.9): very high risk. Obese III (40+): extremely high risk. These are WHO international standards.
Why are there three obesity classes?
Health risks increase significantly within the obese range. A person with BMI 31 has meaningfully different risks than someone with BMI 42. The three classes help healthcare providers tailor interventions: lifestyle changes for Class I, medication for Class II, and surgical consideration for Class III.
Are BMI categories the same worldwide?
The WHO standard is used internationally, but some regions have adjusted cutoffs. For example, in many Asian countries, overweight starts at BMI 23 and obese at 25 (vs. 25 and 30 globally), because Asian populations tend to develop metabolic complications at lower BMIs.

Medical disclaimer: BMI is a screening tool, not a medical diagnosis. It does not measure body fat directly and does not account for muscle mass, bone density, age, sex, or ethnicity. Consult a healthcare provider for personalized health advice.

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