Body Mass Index (BMI) Calculator

About this calculator

Body mass index (BMI) is a simple screening measure calculated as weight in kilograms divided by height in metres squared (BMI = kg/m²). The World Health Organization's standard adult categories are underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (30 and above), though these thresholds are population-level guidelines rather than individual diagnoses.

Doctors, public health researchers, and insurers use BMI as a quick, low-cost way to screen large populations for weight-related health risk, since it correlates reasonably well with body fat at a population level without needing specialized equipment. It has well-known limitations for individuals, though — it doesn't distinguish muscle from fat, so very muscular people can register as "overweight" despite low body fat, and it doesn't account for where fat is distributed on the body.