What the BMI Calculator Does
The Body Mass Index (BMI) Calculator is a standardized screening metric designed by Belgian polymath Adolphe Quetelet and endorsed worldwide by the World Health Organization (WHO). It evaluates whether an individual's body weight falls into a healthy statistical range relative to their physical height.
This client-side tool provides instant calculation across both International Metric (centimeters and kilograms) and US Customary / Imperial (feet, inches, pounds) units. In addition to computing your numerical score, it maps your result onto a visual color-coded risk meter and calculates your ideal target weight range.
How to Calculate Your BMI
- Select Measurement Unit: Choose between Metric (cm, kg) or Imperial (feet, inches, lbs).
- Enter Your Height and Weight: Input your accurate measurements.
- Review the Classification: The tool instantly outputs your score, category badge, and position along the spectrum from Underweight to Obese.
- Check Ideal Weight Bounds: Compare your current weight against the recommended target weight range calculated for your exact height.
Worked Example
Measurements: Height = 175 cm (1.75 m) | Weight = 70 kg.
Metric Formula: $\text{BMI} = \frac{\text{Weight (kg)}}{[\text{Height (m)}]^2} = \frac{70}{1.75 \times 1.75} = \frac{70}{3.0625} \approx 22.86$
Result: 22.9 BMI → Category: Normal Weight (Healthy). Target normal weight range: 56.7 kg to 76.3 kg.
WHO International Classification Table
| Classification | BMI Range (kg/m²) | Health Risk Profile |
|---|---|---|
| Underweight | < 18.5 | Risk of nutritional deficiency, weakened immunity |
| Normal Weight | 18.5 – 24.9 | Lowest statistical risk of cardiovascular illness |
| Overweight | 25.0 – 29.9 | Moderate elevation in hypertension and blood sugar risk |
| Obesity (Class I–III) | ≥ 30.0 | High risk of metabolic syndrome and coronary issues |