Before you order curtains, shutters, or shades, or before you buy materials to make your own, you need to take accurate window measurements to determine exactly what you will need.
Note: measure each window individually - even if they look like they are the same size. There can be small variations.
1. Using a quality tape measure, first measure the window WIDTH:

For inside mounted shades and shutters measure the width inside the window frame.
For outside mounted shades and shutters measure the width from the outside of each side of the molding. If you want the shade or shutter to extend beyond the width of the molding, make sure you measure to include the desired width.
For curtains you will want to have the curtain rod extend past the outside molding to allow room for the curtains to stack back when open. This will allow full view and light from the window and will create an illusion that the window is larger than it is. The extra space required for stack back will depend on the the size and thickness of the curtains but a rule of thumb is
Measure the width of your window outside the molding and add the required stack back allowance.
2. Then measure the window LENGTH:
For inside mounted shades and shutters measure the length inside the window frame.
For outside mounted shades measure the length allowing 2 - 4" above the outside molding - to allow more glass to show when the shade is open - to the outside of the bottom molding.
For outside mounted shutters measure the length from the outside of the top molding to the outside of the bottom molding.
For curtains first determine if you are going to hang your curtains from ceiling height, halfway between the window and ceiling, or just above the window frame (allow 1" above the molding). Then determine your length.
Taking accurate window measurements will ensure that your curtains, shades, or shutters fit. Remember the old carpenter's adage - measure twice, cut once.