BMI Calculator

For most adults, the World Health Organization defines a BMI of 18.5–24.9 as normal weight, though BMI doesn't account for muscle mass, age, or body composition.

Not always — muscle weighs more than fat, so very muscular people can show a high BMI while carrying low body fat. BMI is a general population screening tool, not a diagnosis.

Weight in kilograms divided by height in metres squared. If you enter feet/inches and pounds, they're converted to metric first — the result is shown in both unit systems either way.

BMI itself doesn't use age or gender in its calculation, but both are optional inputs that unlock a more specific interpretation: children and teens (ages 2–19) are assessed against CDC growth-chart percentiles instead of the flat adult categories, adults get thresholds adjusted for sex and for age 65+, and the estimated resting calorie burn (BMR) and ideal weight estimate both need age/gender to be shown at all.

For ages 2–19, BMI on its own isn't meaningful the way it is for adults — the same BMI can be perfectly healthy at one age and a concern at another as kids grow. So instead of the fixed 18.5/25/30 adult cutoffs, a child's BMI is compared against CDC percentile charts for their exact age and sex, showing roughly where they fall relative to other children the same age.

Ideal Weight (Devine formula) estimates a reference weight from your height and sex. BMI Prime is your BMI divided by 25, the upper edge of "normal" — a value under 1.0 means you're under that line, over 1.0 means above it. "To reach normal range" shows how much you'd need to gain or lose from your current weight to land inside 18.5–24.9, or confirms you're already there.