There's a reason why we focus mostly on drum lampshades, here at I like that lamp - they are by far the simplest to measure and make! However, if you want to make a tapered lampshade (or upgrade an old one) with our pre-cut adhesive styrene sheets, you'll want to know what size sheet to order. Simply measuring the height and width of your lampshade won't give you an accurate measurement, as the piece of styrene you need to create the shade will be in the shape of an 'arc', rather than a regular rectangle. So, here's how to determine the required dimensions of your tapered lampshade.
When your styrene sheet arrives, use the paper model to trace your arc onto the styrene. Remember that you need an extra inch for the length of styrene, to allow for overlap when constructing the shade. This extra inch is already figured into the dimensions of the pre-cut styrene.