BMI Calculator
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What is BMI?
Body Mass Index (BMI) is a simple numerical measure derived from a person's weight and height. It is widely used by healthcare professionals as an initial screening tool to categorise individuals into weight status groups: Underweight, Normal weight, Overweight, and Obese. A single BMI value does not diagnose health conditions, but it provides a useful quick reference for assessing weight-related health risks.
BMI Formula
Metric: BMI = Weight (kg) / Height (m)²
Imperial: BMI = (Weight (lbs) / Height (in)²) × 703
Imperial: BMI = (Weight (lbs) / Height (in)²) × 703
The calculator accepts both metric (kilograms and centimetres) and imperial (pounds, feet, and inches) inputs, converting automatically to produce your BMI.
BMI Categories (WHO Standard)
Below 18.5 — Underweight
18.5 – 24.9 — Normal weight
25.0 – 29.9 — Overweight
30.0 and above — Obese
18.5 – 24.9 — Normal weight
25.0 – 29.9 — Overweight
30.0 and above — Obese
Example Calculation
Weight: 70 kg
Height: 170 cm (1.70 m)
BMI = 70 / (1.70)² = 70 / 2.89 = 24.2 — Normal weight
Height: 170 cm (1.70 m)
BMI = 70 / (1.70)² = 70 / 2.89 = 24.2 — Normal weight
Important Notes
- Screening only — BMI is a screening tool, not a diagnostic measure. Consult a doctor for a full health assessment.
- Does not distinguish fat from muscle — Athletes may have a high BMI due to muscle mass, not excess fat.
- Age and sex — BMI ranges may differ for children, elderly individuals, and pregnant women.
- Ethnicity — Some health bodies use adjusted cutoffs for different ethnic groups.
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