In our Stick and Tissue models we sometimes want to build a model in a smaller or larger size.  We usually take the plan down to a Kinko's or Printers shop and ask them resize the model plans for us.  One of the first things they ask, "What percentage do you want us to print it to?"

We usually use the wing span to determine the size we're looking for and try to determine what that percentage will be, up or down.  For those of us who aren't a real mathematician (Me) here's a link to a site that allows you to put in the original size span and the desired size span and it works out the percentage for us.
Click Here