Picking a Shutter Size
Designing for your windows is entirely up to you and what kind of look you want to acheive. To acheive the look of a functioning shutter, it is recommended that the shutter width should be 1/2 the width of your entire window. When designing your shutters for accenting the window, you want to be sure the shutter size is not too wide as to overpower the window.
To determine the right length for your shutters you simply measure the length of the window, not including the frame. That will be your shutter length. Remember some shutters are available in 1/4" increments so you can choose the closest length.