What is Body Mass Index (BMI)?
Body Mass Index (BMI) is a standardized anthropometric screening metric that estimates body
composition by comparing an individual's weight against the square of their height. Devised
in the 19th century by Belgian polymath Adolphe Quetelet, it is widely utilized by the World
Health Organization (WHO) and public health organizations as an accessible initial indicator
of weight categories.
BMI establishes four broad baseline categories for adults aged 20 and older:
- Underweight: BMI less than 18.5 kg/m²
- Normal / Healthy Weight: BMI between 18.5 and 24.9 kg/m²
- Overweight: BMI between 25.0 and 29.9 kg/m²
- Obese: BMI of 30.0 kg/m² or higher (divided into Class I, II, and III
obesity)
How to Use the BMI Calculator
Evaluate your body mass index in four simple steps:
1
Select Unit System
Choose between Metric (centimeters and kilograms) or Imperial
(feet, inches, and pounds).
2
Enter Standing Height
Input your height barefoot standing straight against a flat
vertical wall.
3
Input Current Weight
Provide your current morning weight using a calibrated digital
bathroom scale.
4
Review Category
Inspect your resulting score, classification band, and estimated
healthy weight bracket.
BMI Mathematical Formulas
Mathematical calculations used to evaluate Body Mass Index in metric and imperial measurement
systems:
Example Calculation Walkthrough
Consider an adult individual with a height of 175 cm (1.75 meters) and a
weight of 70 kilograms:
- Recorded Height 175 cm (1.75 meters)
- Height Squared (1.75 × 1.75) 3.0625 m²
- Recorded Weight 70.0 kg
- Calculation (70 ÷ 3.0625) 22.857 kg/m²
- Rounded BMI Result 22.9 kg/m²
- WHO Classification Normal / Healthy Weight (18.5 to 24.9)
