Health & Nutrition
Body Mass Index (BMI)
Updated 2025-09-02
Definition
A screening metric that divides weight in kilograms by height in meters squared (kg/m²). The World Health Organization classifies adults as underweight (below 18.5), healthy weight (18.5-24.9), overweight (25-29.9), or obese (30+). BMI is a cheap, fast population-level proxy for body fatness, but it does not distinguish muscle from fat and can misclassify lean athletes as overweight. Most clinicians now pair BMI with waist-to-hip ratio or direct body fat measurements for individual assessments.
Primary source: CDC BMI overview
Related Calculators
- BMI Calculator - Calculate your Body Mass Index (BMI) from height and weight. See where you fall on the BMI scale.
- Body Fat Percentage Calculator - Estimate your body fat percentage using the US Navy method based on body measurements.