Cinema screen size calculator

Cinema pictures come in two shapes: scope, 2.39:1, and flat, 1.85:1 (see aspect ratio). A screen is masked for one of them and opens or closes its masking for the other.

• Constant height: both formats share the full screen height and scope is wider. The side masking opens for scope. Most new auditoriums are built this way, because the widest format gets the biggest picture.
• Constant width: both formats use the full width and flat is taller. The top masking comes down for scope. You find it in older and narrower rooms.

The calculator fits the largest picture of each shape inside the maximum width and height you enter. It then measures the horizontal angle the scope picture fills from the front and back rows, and divides the scope width by the DCI scope frame (2,048 pixels across at 2K, 4,096 at 4K) to give the size of one pixel on the screen. Those frame sizes are the ones the ISDCF lists from the SMPTE standards: scope is 2048 × 858 at 2K and 4096 × 1716 at 4K, flat is 1998 × 1080 and 3996 × 2160.

Screen width sets the rest of the room. It tells you how much light you need (try the screen brightness calculator and our projector buying guide). It also sets where the first row can go, and from there how many rows fit at 1,200 mm or more each. Draw those rows, the aisles and the wheelchair spaces in the seat plan builder. If you are converting to recliners, plan the rows again from the start: the UNIC handbook gives recliner depths of 900 to 1,400 mm upright and 1,800 mm or more fully reclined.

For what national seat counts look like, the average screen has 180 seats in France, 162 in Australia and 159 in Germany. Our movie theater counts by country has the figures and their sources.