Projector Throw Distance Calculator

How it is calculated

The tool assumes a 16:9 screen. For that shape the width is a fixed share of the diagonal, width = diagonal × 16 ÷ √337 (about 0.8716 × the diagonal), because 16² + 9² = 337. The projector distance is then distance = width × throw ratio. The diagonal is entered in inches and the throw ratio is the plain number from the projector's spec (1.5 for 1.5:1). Results are screen width in centimetres (one decimal) and the projector distance in metres and in feet (two decimals each). Both inputs must be above zero. Other screen shapes such as 4:3 or 16:10 are not handled, and the distance is measured from the lens to the screen, so it is only valid for the projector's fixed-ratio setting, not a zoom range.

Common mistakes

• Entering the screen width instead of the diagonal; the field is the diagonal, so a 105-inch wide screen is about a 120-inch diagonal.
• Using a 4:3 or 16:10 screen size: the width calculation is for 16:9 only, so the distance will be off for other shapes.
• Typing the throw ratio as 1:5 or 15 instead of 1.5; the ratio is distance divided by width, written as one number.
• Ignoring that many projectors have a zoom lens, so the spec lists a range such as 1.4–2.2; use one end of the range and you get the nearest or furthest placement, not the only one.
• Measuring the distance from the projector body or from the ceiling mount bracket instead of from the lens to the screen surface.