The scale calculator will easily transform the object you've purchased into a pattern that will fit the wood thickness you've purchased. What it doesn't do is transform the piece into a size that you want. So if you want to purchase say a house from MakeCNC and you want to use that as a piece of terrain for a miniatures game. The game uses 10mm miniatures but the house you purchased is say 3" tall. That pattern won't be adjusted by using the scale calculator. However, you can calculate the scale change if you know how tall the building is, and how tall you want the building to be. To do that you'd figure out how tall you want the building and scale down the width and height of the building to match. you will then have to go into the pattern and change the width of the connections to match your wood thickness. You can do that by ungrouping the pattern. Then set the (inscape) the selection tool to node. Now you can see where the nodes are. Using the mouse pointer you click outside of the node area and drag your pointer over the nodes to highlight the left side (or right) of the nodes you want to move. Then you select the X (assuming the space you want to move is on the horizontal) and move the X over to the left how ever much you need for it to change the distance between the space where the parts connect to match your wood's thickness. Hope that helps.