Body mass index is a quick screen that relates your weight to your height. It doesn't measure body fat directly, but it's a useful, standardized starting point for a conversation about healthy weight ranges.
How BMI is calculated
In metric units, BMI is your weight in kilograms divided by the square of your height in meters. The imperial version multiplies pounds over inches-squared by 703 to reach the same number.
The calculator above accepts either unit system — switch the toggle and enter height and weight in the matching units.
Reading the categories
The World Health Organization groups adult BMI into underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (30 and above).
BMI has real limits: it can't tell muscle from fat, and it isn't tailored to age, sex, or athletic build. Use it as a rough indicator, not a diagnosis, and talk to a clinician about what's right for you.