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BMI Formula:
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Body Mass Index (BMI) is a simple index of weight-for-height that is commonly used to classify underweight, normal weight, overweight and obesity in adults. It is calculated by dividing a person's weight in kilograms by the square of their height in meters.
The calculator uses the standard BMI formula:
Where:
Explanation: The formula provides a simple numeric measure of a person's thickness or thinness, allowing health professionals to discuss weight problems objectively with their patients.
Details: BMI provides the most useful population-level measure of overweight and obesity as it is the same for both sexes and for all ages of adults. However, it should be considered a rough guide because it may not correspond to the same body fat percentage in different individuals.
Tips: Enter weight in kilograms and height in meters. For height, you can convert from centimeters by dividing by 100 (e.g., 175 cm = 1.75 m). All values must be valid (weight > 0, height > 0).
Q1: What are the standard BMI categories?
A: For adults: Underweight (<18.5), Normal weight (18.5-24.9), Overweight (25-29.9), Obese (≥30).
Q2: Is BMI different for women and men?
A: The same BMI ranges apply to both women and men. However, women tend to have more body fat than men at the same BMI.
Q3: What are the limitations of BMI?
A: BMI doesn't account for muscle mass, bone density, overall body composition, and racial/ethnic differences. Athletes may have a high BMI due to increased muscle rather than fat.
Q4: How does BMI differ for children?
A: For children and teens, BMI is age- and sex-specific and is referred to as BMI-for-age. This calculator is for adults only.
Q5: What is a healthy BMI range for Australian women?
A: The healthy BMI range is the same worldwide: 18.5 to 24.9. However, individual health assessments should consider other factors.