Projector Screen Size Calculator

This works out the three distances that decide a projector setup: the width and height behind a screen diagonal, how far back the projector has to sit, and where the seats belong. Enter the diagonal and aspect ratio with the throw ratio from the projector's spec sheet, or start from the room instead and get the largest image that fits the distance you have. Seating comes from the horizontal viewing angle, with the 30 degree SMPTE reference and the 26 to 36 degree band THX publishes marked out. Lens shift and vertical offset are not modelled, so this tells you how far back the projector goes and not how high to hang it.