Throw Ratio Projector throw ratio (distance-to-width ratio, D/W)

What throw ratio is

Throw ratio ties a projector's distance to its picture size. Wikipedia defines throw as the distance between the projector lens and the screen, given as a ratio that relates the distance to the screen width, assuming the image fills the screen. The formula is R = D / W, and rearranged, D = W times R. Distance is measured from the front of the lens. BenQ reads the same number the plain way: at a ratio of 2.0, the projector must be 2 feet away for every 1 foot of image width. Because it is a ratio, the same number works in feet, meters or inches, as long as both measurements share a unit.

Throw ratio is a property of the lens, not the projector body. Wikipedia notes that most lenses are zoomable across a range of ratios, while fixed lenses sit at one, and that larger, more expensive projectors can accept a variety of lenses. So a spec sheet usually lists two numbers, the ratio at minimum zoom and the ratio at maximum zoom, and BenQ adds that some specs also list a figure with no zoom applied.

How zoom shows up in the numbers

The zoom factor is just the larger ratio divided by the smaller. The Epson Home Cinema 5050UB lists a throw ratio of 1.35 to 2.84 with a 2.1x powered zoom (2.84 ÷ 1.35 is 2.1). The JVC DLA-NZ8's own spec sheet lists 1.43 to 2.92 on a 2x zoom and rates it for 60 to 200 inch diagonals, and ProjectorCentral lists the Sony VPL-XW5000ES at 1.38 to 2.21 with a 1.6x manual zoom (2.21 ÷ 1.38 is 1.6). Standard home theater projectors therefore fill a given screen from a distance range, not a single spot, and that range is what makes ceiling mounting forgiving. The range also has edges: the 5050UB throws a 100-inch image from 20.6 feet at 2.84 and from 9.8 feet at 1.35, so a room shorter than 9.8 feet cannot fill 100 inches at all.

BenQ cautions that zooming can affect image quality and recommends, for a fixed mount, picking a projector whose ratio fits without leaning on the zoom ratio. See lens shift for the other half of fitting a projector into a room.

Short throw, ultra-short throw and long throw

ProjectorCentral defines a short throw projector as one whose lens has a throw ratio of 0.4 or less, and Wikipedia gives the same threshold. That cutoff is an industry convention, not a standard. Ultra-short-throw designs go far below it: the Samsung Premiere LSP9T has a throw ratio of 0.189, and Samsung says it can project a 100-inch image from 4.4 inches away from the wall. The Hisense PX3-Pro lists a throw ratio of 0.22 for 80 to 150 inch images. At the other end, Wikipedia gives a long-throw lens ratio of 7.5 as an example of a projector that must sit far back. See ultra-short-throw projector for the screen and placement rules those models need.

Marketing labels do not always match the 0.4 line. BenQ calls its X500i a short throw projector that needs 5 feet for a 100-inch image, against 8.2 feet for the standard-throw X3100i. A 100-inch 16:9 image is 87.2 inches, or 7.27 feet, wide, so those distances imply ratios of about 0.69 and 1.13. The X500i is short throw by BenQ's naming and not by the 0.4 definition.

Worked example: 120-inch screen and a 14-foot room

Start with the screen. A 120-inch 16:9 screen is 104.6 inches, or 8.72 feet, wide. Multiply by each ratio to get the distance range. The Epson 5050UB at 1.35 to 2.84 reaches the screen from 11.8 to 24.8 feet. The JVC NZ8 at 1.43 to 2.92 works from 12.5 to 25.5 feet. The Sony XW5000ES at 1.38 to 2.21 works from 12.0 to 19.3 feet. A 14-foot throw fits all three, but a 10-foot room fits none of them.

Reverse it when the distance is fixed. At 14 feet the Epson fills any width from 14 ÷ 2.84 = 4.93 feet to 14 ÷ 1.35 = 10.37 feet, which is a 68-inch to 143-inch diagonal on a 16:9 screen. For an ultra-short model the same formula gives short distances: a 150-inch image on the Hisense is 130.7 inches wide, so the lens sits 130.7 × 0.22 = 28.8 inches from the screen. Samsung's quoted 4.4 inches is measured from the wall, a different reference point than the lens-to-screen distance D, so use each maker's placement chart. The projector throw tool runs these calculations for you.

Common confusions

Throw ratio is not throw distance. The ratio is a fixed property of the lens; the distance depends on how big a screen you choose, so a 2.0 ratio needs 10 feet for a 5-foot-wide screen and 20 feet for a 10-foot-wide one. A lower ratio does not mean a better projector, and neither does a higher one. And throw ratio says nothing about brightness: a bigger image spreads the same lumens over more area, which is why a long-throw setup on a very large screen needs the light budget worked out in foot-lamberts. Throw ratio also does not tell you where the image lands vertically; that is lens shift and offset, covered in keystone correction.