Throw ratio

Throw ratio is a simple formula: the distance from the projector lens to the screen, divided by the width of the resulting image. A throw ratio of 1.5 means the projector needs to sit 1.5 times the image width away from the screen. Standard-throw projectors typically fall between 1.2 and 2.0, short-throw units sit well under 1.0, and ultra-short-throw models can produce a large image from just inches away.

Knowing your room depth before buying a projector avoids a lot of frustration. A standard-throw model in a small room may force you to shrink the image far below what the projector is capable of, while a short-throw unit gives more flexibility for placing the projector on a low shelf or media console near the screen instead of mounting it on the back wall.

A common mistake is buying a projector based on brightness or resolution specs alone and only measuring the room afterward, which can mean the image is stuck far smaller or larger than planned. Zoom lenses give some flexibility, but every projector still has a throw ratio range it cannot go outside, so checking that range against the room is a first step, not an afterthought.