Body Mass Index (BMI) Calculator

How to use

1. Enter current weight in kilograms.
2. Enter standing height in centimeters.
3. Review computed BMI score (kg/m²).
4. Check your designated WHO weight category.
5. Identify your optimal healthy weight threshold for normal BMI (18.5–24.9).

BMI Quetelet formula and mathematics

The Body Mass Index is calculated via the Quetelet equation: BMI = Weight (kg) / [Height (m)]².

For example, an individual weighing 80 kg at 175 cm height: 80 / (1.75 × 1.75) = 26.12 kg/m², which classifies into the overweight bracket.

WHO international BMI classifications

• Under 16.0 — Severe thinness.
• 16.0 to 16.9 — Moderate thinness.
• 17.0 to 18.4 — Mild thinness.
• 18.5 to 24.9 — Normal healthy weight.
• 25.0 to 29.9 — Pre-obesity / Overweight.
• 30.0 to 34.9 — Class I Obesity.
• 35.0 to 39.9 — Class II Obesity.
• 40.0 and above — Class III Severe Obesity.

Clinical limitations of BMI screening

• Muscular density skew: athletic powerlifters and sprinters register false "overweight/obese" flags due to contractile muscle mass.
• Age-related sarcopenia: older adults may possess normal BMI despite elevated hidden visceral adiposity.
• Inapplicable during pregnancy or lactation.

Targeting a healthy weight baseline

Normal weight corresponds to the 18.5 to 24.9 BMI zone. For 175 cm stature, healthy weight spans from 56.7 kg to 76.3 kg.

Always combine BMI with waist circumference or body fat estimates for comprehensive health evaluation.