

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 handheld calculator:
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). 

For more detailed instructions, see Use and Interpretation of the WHO and CDC Growth Charts for Children from Birth to 20 Years of Age in the United States. 
Flash calculator (requires Flash 5 plugin) 
