How Does the BMI Calculator Work?
The Body Mass Index (BMI) is an internationally recognized anthropometric metric formulated by Belgian statistician Adolphe Quetelet. It quantifies an adult individual’s body mass relative to their height to screen for weight categories that may correlate with potential health complications.
The World Health Organization (WHO) classifies adult BMI as follows:
- Underweight: BMI less than 18.5
- Normal weight: BMI between 18.5 and 24.9
- Overweight: BMI between 25.0 and 29.9
- Obesity Class I: BMI between 30.0 and 34.9
- Obesity Class II & III: BMI 35.0 or greater
Formula & Mathematical Methodology
BMI is computed using either metric or imperial units:
Metric Units:
BMI = Weight (kg) / [Height (m)]²
Imperial Units:
BMI = [Weight (lbs) × 703] / [Height (inches)]²
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Step-by-Step Practical Calculation Example
Consider an adult who weighs 72 kg and stands 175 cm (1.75 meters) tall:
- Height in Meters: 1.75 m
- Height Squared: 1.75 × 1.75 = 3.0625 m²
- Calculation: 72 / 3.0625 = 23.51 kg/m²
- Classification: Normal Weight (Healthy)