BMI Calculator

Body mass index from height and weight, with the WHO category.

Overview

Calculates Body Mass Index (BMI) from body weight and height, categorizing adult physical health against World Health Organization clinical cutoffs.

Formula & Calculation Method

BMI = Weight (kg) / [Height (m)]^2

Weight in kilograms divided by the square of height in meters. WHO adult classifications: Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), Obese (≥30).

Worked Example: Adult Weighing 72 kg at 175 cm Height

Inputs: Weight = 72 kg | Height = 175 cm (1.75 meters)

  • Height squared = 1.75 × 1.75 = 3.0625 m²
  • BMI value = 72 / 3.0625 = 23.51 kg/m²
  • Clinical classification = Normal Weight (Healthy Range)

Summary: Weight = 72 kg | Height = 175 cm | BMI = 23.5 kg/m² | Category = Normal Weight

Common Use Cases

  • Clinical Screening: Screen for weight-related epidemiological risks including hypertension and type-2 diabetes.
  • Weight Loss Milestones: Determine the exact kilogram target needed to enter the recommended healthy weight range.
  • Annual Health Checkups: Track annual biometric changes alongside blood lipid panels and waist measurements.

Frequently Asked Questions

Why is BMI misleading for athletes?

BMI cannot distinguish between dense muscle mass and adipose fat tissue; heavily muscled individuals often score in the overweight range despite low body fat.

What are the revised BMI cutoffs for South Asians?

Due to higher visceral fat propensity, WHO guidelines recommend Asian cutoffs: Normal (18.5–22.9), Overweight (23.0–27.4), and Obese (≥27.5).

At what BMI does health risk significantly increase?

Cardiovascular and metabolic risks increase progressively when BMI exceeds 25, accelerating rapidly above 30.

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