# BMI Calculator

> Calculate BMI, BMI Prime, ponderal index, adult category, and the corresponding healthy-weight range in metric or imperial units.

Page: https://askcalculators.com/calculator/bmi-calculator/
Definition: https://askcalculators.com/calculator/bmi-calculator/definition.json
JSON Schema: https://askcalculators.com/calculator/bmi-calculator/schema.json
Version: 20.1.0
Maintained by: AskCalculators (software project; not a credentialed reviewer)
Qualified review: pending. Automated checks do not establish professional approval.
Page status: Live
Review status: Pending

## Use
Open the calculator page and enter values. Query-string parameters can restore and bookmark a calculation.
Example: https://askcalculators.com/calculator/bmi-calculator/?unitSystem=metric&sex=male&age=30&weightKg=70&heightCm=175

## Inputs
- unitSystem: Units; type=select; required; default=metric; values=metric|imperial
- sex: Sex used by equation; type=select; required; default=male; values=male|female
- age: Age; type=number; required; default=30; min=13; max=120
- weightKg: Weight; type=number; required; default=70; min=1; max=500; showWhen=unitSystem:metric
- heightCm: Height; type=number; required; default=175; min=50; max=300; showWhen=unitSystem:metric
- weightLb: Weight; type=number; required; default=154; min=2; max=1100; showWhen=unitSystem:imperial
- feet: Height feet; type=number; required; default=5; min=1; max=9; showWhen=unitSystem:imperial
- inches: Height inches; type=number; required; default=9; min=0; max=11.9; showWhen=unitSystem:imperial

## Outputs
- bmi: BMI; format=number; primary
- category: Screening category; format=text
- healthyRange: BMI 18.5–24.9 weight range; format=text
- bmiPrime: BMI Prime; format=number
- ponderalIndex: Ponderal index; format=number

## Formula
BMI = weight (kg) ÷ height² (m²); BMI Prime = BMI ÷ 25; ponderal index = weight ÷ height³.

## Rules
- Empty optional inputs are undefined, not zero.
- Hidden conditional inputs are ignored.
- Do not invent missing required inputs.

Notice: BMI is a screening measure, not a diagnosis. People under age 20 require age- and sex-specific growth-chart percentiles.