For a quick answer, snap a photo and call us! If you still have the old shade, it's easy - pick one as close in size as you can. If you'd like to swap shapes, stick within 1-1 1/2" of the height and width. We ship a free harp with every replacement lamp shade order so that it insures our shade will fit your base properly. The bottom of the shade will land just below the socket, where it should. With today's LED bulbs that do not get hot, the bulb(s) can be closer to the interior of the shade than ever before. Hence, there are a lot more options, but you do want it to look proportionally correct. Height: The rule of thumb is that the shade should be app 2/3rds the height of the lamp body. Width: The width of the shade should not be less than the width of the base at its widest point. I think it should be slightly larger 1-2" to look and feel correct. Here's a quick test: Cut a piece of cardboard the dimensions of the shade, as a flat silhouette. Tape it to the bottom of the socket, stand back and see what you think. If you have the time, keep it there for a day or two to get used to it. This is particularly helpful if you are thinking of changing shapes.