Measure the top diameter across the widest part of the top opening
Measure the bottom diameter across the widest part of the bottom opening
Measure the slant height from the top edge to the bottom edge along the side
Measure the vertical height from the top opening to the bottom opening
Measure the fitter size if the shade attaches with a harp, clip, or socket ring
Measure the inside opening if the shade has a washer, uno, or clip-on fitting
Measure the widest point of the shade if it is not a standard shape
Measure the width and depth separately if the shade is oval or rectangular
Measure from seam to seam if the shade has a hard frame
Record all measurements in inches or centimeters consistently