BMI Calculator
Body Mass Index in seconds. Metric or imperial, WHO categories included.
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cm
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⚠️ Medical disclaimer: BMI is a screening tool, not a diagnosis. It does not account for muscle mass, bone density, or fat distribution. Consult a healthcare professional for a complete assessment.
How the BMI Calculator Works
Enter your weight and height in either metric (kg, cm) or imperial (lb, ft + in) units. The calculator uses the standard WHO formula: BMI = weight (kg) ÷ height² (m²).
Your result is color-coded against the four WHO categories: Underweight (< 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (≥ 30). A medical disclaimer is included as BMI is a screening tool, not a diagnosis.
Frequently Asked Questions
What is the BMI formula?
BMI = weight in kilograms ÷ (height in metres)². For imperial units, the calculator first converts lbs to kg and inches to cm before applying the formula.
Is BMI accurate?
BMI is a useful population-level screening tool, but it has known limitations. It does not distinguish between fat and muscle, and may misclassify athletes (high muscle mass) or elderly individuals (lower muscle mass). Use it as a starting point, not a definitive health measure.
What are the WHO BMI categories?
The WHO defines four main categories: Underweight (BMI < 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (≥ 30). Obesity is further divided into Class I (30–34.9), Class II (35–39.9), and Class III (≥ 40).
Does BMI apply to children?
Adult BMI categories do not apply to children and teens. Pediatric BMI uses age- and sex-specific percentiles. This calculator is designed for adults aged 18 and older.
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