A four-foot work is either horizontal or vertical. Horizontal, the left and right sides can be wider, and the upper and lower sides are generally less. Vertical antonym.
Therefore, after adding a picture frame, it is generally enough to extend from the edge of the picture core 10 cm or about 20 cm. Depending on whether the work is horizontal or vertical.
The size of this frame is generally not fixed and is subject to the framer. Of course, he won't give you a particularly big edge, which will waste materials. It's not too narrow for you and it looks ugly. You still have to ask the framed one.
You can measure the up, down, left and right dimensions of the painting place at home in advance and tell the framer. He will do it himself.