6. Calculating BMI using the metric system

	Formula: weight (kg) / [height (m)]2 Calculation: [weight (kg) / height (cm) / height (cm)] x 10,000

With the metric system, the formula for BMI is weight in kilograms divided by height in meters squared. Since height is commonly measured in centimeters, an alternate calculation formula, dividing the weight in kilograms by the height in centimeters squared, and then multiplying the result by 10,000, can be used.

When using a hand-held calculator:

  if your calculator has a square function, divide weight (kg) by height (cm) squared, multiply by 10,000 and round to one decimal place.

  if your calculator does not have a square function, divide weight by height twice as shown in the calculation formula above, multiply by 10,000 and round to one decimal place.

Calculations for BMI can be completed as a continuous equation. (Note that the formula for the latter calculation is on the CDC Clinical Growth Charts and will be the calculation used in this module).

	Example: We know that Sam’s weight is 16.9 kg and his height is 105.4 cm. What is Sam’s BMI? (16.9 kg / 105.4 cm / 105.4 cm ) x 10,000 = 15.2

For more detailed instructions, see Using and interpreting the CDC Growth Charts, Step 4. Calculating BMI.