Theater seats come in a variety of widths, depending on the age of the theater, the space available and the target audience. High-end theaters may have luxury seating that is wider than the cushions at your local multiplex. Movie theaters may also differ from live theater spaces in seat width. If you are unable to simply take a measuring tape with you to measure the seat width, there are a number of ways you can approximate how wide the seats are at a particular theater.
Look for technical specifications on the theater's website. Stage theaters will often have a link that provides information to groups renting out the theater. Search for the words "Ground plan" in the technical specifications, and if you find a ground plan document, download it. Ground plans have scale drawings of the stage and often include seating as well. Look for the scale, which will tell you whether 1/8, 1/4 or 1/2 inch on the drawing equals 1 foot of real space. Print the drawing, making sure your printer is not set to shrink the drawing to fit the paper, then measure a seat image. Calculate for the scale, so if 1/8 inch equals 1 foot and the seat is 3/16 inches wide, that translates to 1.5 feet.
Call the theater if you need exact measurements of the seat width. Make sure you don't call during busy hours, and expect to leave your name and number and wait for a call back, as the theater may be in the middle of a showing. Specify whether you want the measurement of the cushion width only, or if you want one or both arms included.
Look up when the theater was built or remodeled. Standard seat width varies between 18 and 22 inches, but older theaters, such as historic movie houses from the 1940s and earlier, may have 15- to 16-inch seats. A more recent remodeling may mean wider seats, but this can't be confirmed without visiting the theater. If the theater or local newspapers note that the seating has been upgraded, or the theater advertises "luxury seating" or "extra wide seats," the seats may be 24 to 26 inches wide.