This simple guide will ensure your artwork is measured accurately so your picture frames fit well.
First lay your picture on a flat work surface. Check with a set square to see if you picture is square. If it is not you will need to measure the shortest lengths if you want the picture to display without unfinished edges or white showing.
A mount is a PH neutral card into which is cut an opening. The measurements you make for your window will need to be reduced on each length by 5 mil. Framing and mounting is not the most precise art and to avoid errors this 5 mil leeway is included to make sure the mount overlaps the desired image.
Common framing methods work from the image outwards unless of course you are trying to make a picture fit within a ready frame. The final size of the frame is determined by the size of the picture plus a surround of mount card. The area left for the mountcard is a personal choice but on most medium sized framing jobs is typically between 45 mil and 50 mil.
Always add an extra 5 mil to the base of the surrounding mountcard and you will then arrive at the overall size of the framed picture excluding the width of the molding chosen.