Health & Fitness
BMI Calculator
Calculate your Body Mass Index and see your weight category instantly.
Medical Disclaimer: This calculator is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making health decisions.
Frequently Asked Questions
What is BMI?
BMI (Body Mass Index) is a numerical value derived from a person's weight and height. It is calculated as weight (kg) ÷ height² (m²) for metric units. It is used as a simple screening tool to categorise weight status: Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), and Obese (≥30).
Is BMI an accurate measure of health?
BMI is a useful screening indicator but has limitations. It does not directly measure body fat or muscle mass. Athletes with high muscle mass may have a high BMI without excess fat. Older adults may have normal BMI but high body fat. Always interpret BMI alongside other health indicators and consult a healthcare professional.
How do I calculate BMI in imperial units?
For imperial units, BMI = (weight in pounds × 703) ÷ (height in inches)². For example: a person weighing 150 lb at 5'7" (67 inches) has BMI = (150 × 703) ÷ (67²) = 105,450 ÷ 4,489 ≈ 23.5 — Normal weight.
What BMI is considered healthy?
According to the World Health Organisation (WHO): Underweight = below 18.5 | Normal weight = 18.5–24.9 | Overweight = 25–29.9 | Obese Class I = 30–34.9 | Obese Class II = 35–39.9 | Obese Class III = 40+. These ranges apply to adults aged 18 and over.
Does BMI differ for children?
Yes. For children and teenagers (ages 2–19), BMI is assessed using age- and sex-specific percentile charts rather than fixed thresholds. The adult BMI ranges on this calculator are not applicable to children. Use a paediatric BMI tool for those under 18.
What should I do if my BMI is outside the normal range?
A BMI outside the normal range is a signal to speak with a healthcare professional — not a diagnosis. Doctors consider BMI alongside blood pressure, cholesterol, blood sugar, waist circumference, and lifestyle factors before making any health recommendations.