Regardless of whether you opt for full height, cafe style or tier on tier shutters, simply measure the width and height of your window inside the frame. Ideally take three measurements for both the width and height. For the width: measure the width of the window across the top, across the middle and across the bottom. For the height: measure the height of the window on the left, in the centre and on the right.
Provide us with the smallest measurement you get out of the three for the width and the smallest measurement you get out of the three for the height.