To size a chandelier for your dining room, foyer, or a centerpiece of a room, measure the length and width of the room and add those figures together. The sum, converted to inches, will equal the diameter that you can use as a guideline when selecting the size of your chandelier. For example: If your room is 16ft by 20ft, then 16+20=36, and the correct size for your chandelier is 36 inches diameter. When installing a chandelier above a dining or kitchen table, the chandelier should be approximately three-quarters the width of your table. The bottom of your chandelier should be approximately 30 inches above the surface of your table.