BMI Calculator
BMI Calculator
Calculate your Body Mass Index using metric or imperial units.
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Understanding BMI
Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is BMI = kg/m2 where kg is a person's weight in kilograms and m2 is their height in metres squared.
A BMI calculation provides a single number that can give a general idea of whether a person has a healthy body weight for their height. It's a widely used screening tool but it does not diagnose body fatness or the health of an individual.
BMI Categories
- Below 18.5: Underweight
- 18.5 – 24.9: Healthy Weight
- 25.0 – 29.9: Overweight
- 30.0 and Above: Obesity
Logic & Formulas
The core formula for Body Mass Index (BMI) is:
BMI = Weight (kg) / [Height (m)]^2
To accommodate imperial units, the calculator first converts all inputs into the metric units required by the formula:
- Height: Total inches from feet and inches are converted to meters.
Height (m) = Total Inches * 0.0254. - Weight: Pounds (lbs) are converted to kilograms.
Weight (kg) = Weight (lbs) * 0.453592. Stone is first converted to pounds (1 st = 14 lbs).
The final BMI result is then categorized based on the standard ranges listed above.