BMI Calculator
Check your Body Mass Index and healthy weight category instantly.
Healthy adult BMI ranges from 18.5 to 24.9 under standard WHO guidance.
What is Body Mass Index (BMI)?
Body Mass Index (BMI) is an epidemiological metric developed in the 19th century by Belgian mathematician Adolphe Quetelet. It provides a simple, accessible calculation comparing an individual’s body mass relative to their height to identify potential weight-related health risks.
The Mathematical BMI Formula
BMI = Weight (in kilograms) ÷ [Height (in metres)]²
Example: An individual weighing 70 kg who is 1.75 m (175 cm) tall:
BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.86 kg/m²
Standard WHO Classification Table
| Category | BMI Range (kg/m²) | Health Risk |
|---|---|---|
| Underweight | < 18.5 | Increased risk of nutritional deficiency and osteoporosis |
| Normal Weight | < 18.5 – 24.9 | Lowest statistical risk for cardiovascular ailments |
| Overweight | 25.0 – 29.9 | Moderate risk for hypertension and type 2 diabetes |
| Obese | ≥ 30.0 | High risk for metabolic syndrome and cardiovascular disease |
Important Note for Asian Indians
Clinical studies endorsed by the Indian Council of Medical Research (ICMR) and the Ministry of Health indicate that South Asians tend to possess a higher percentage of body fat and visceral adiposity at lower body weights. Consequently, revised clinical cutoffs for Indians define overweight as BMI ≥ 23.0 and obesity as BMI ≥ 25.0.
Limitations of the Metric
BMI is a population-level screening gauge, not an individual clinical diagnosis. It cannot distinguish between lean muscle mass and adipose fat. Athletic bodybuilders often register in the "overweight" or "obese" categories despite low body fat percentages. Similarly, elderly individuals may register "normal" despite losing protective skeletal muscle.