BMI Calculator
Calculate your Body Mass Index instantly in metric or imperial units. See your health category and ideal weight range.
Body Mass Index Calculator
What Is BMI and How Is It Calculated?
Body Mass Index (BMI) is a numerical value derived from your weight and height. It's widely used as a screening tool to categorise weight status in adults. The formula is: BMI = weight(kg) ÷ height(m)² for metric, or BMI = 703 × weight(lbs) ÷ height(in)² for imperial units.
BMI Categories (WHO Standard)
Underweight: BMI 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 and above. These thresholds apply to adults aged 18 and over.
Limitations of BMI
BMI is a useful population-level screening tool but has important individual limitations. It doesn't distinguish between fat and muscle mass — athletes with high muscle mass often register as "overweight" despite being very healthy. It also doesn't account for fat distribution, age, or sex differences in body composition. Always consult a healthcare professional for a full health assessment.
A Healthier Approach
BMI works best alongside other measures: waist circumference, body fat percentage, blood pressure, and blood work. A BMI in the "normal" range combined with regular physical activity, a balanced diet, and good sleep habits is generally associated with better long-term health outcomes.