Picture Frame Displays

how big should my frame be for my picture prints?
If I get 16×20 prints, should i get a 16×20 frame or should i go a little bigger? I suppose my question is: Does the 16×20 measurement for the frame refer to the size of the entire frame or just the display part of the frame? Obviously, if the latter is true then getting a 16×20 frame will suffice.
The 16×20 size is usually the size of the opening of the frame to fit artwork that is sized 16×20. If you wish to get the piece matted then get a 20×24 frame with a mat that is 2.25″ all around.
Metal Picture Frame Assembly for Frame Destination Picture Frames