Projector Throw Distance Calculator
Enter the screen size and the projector's throw ratio to get the throw distance, or enter the distance to get the image width you can fill. Top and front drawings show how the image sits on the screen.
How to read the top and front drawings
The drawings above change as you type; the page does not need to reload. The dimensions in the drawings match the numbers in the result.
- Top view: the projector on the left, the screen on the right, and the light spreading out between them. The throw distance and the image width are drawn at the same scale, so a lower throw ratio gives a wider spread and a higher ratio a narrower one. Only the overall size of the drawing changes to fit the display (the scale bar shows the scale). The projector icon itself is not to scale.
- Front of the screen: the size of the image, drawn with its aspect ratio kept. If you enter a screen size, the image and the screen are centered on each other, and the drawing shows whether there is a margin (the image is smaller) or overflow (the image is larger; red hatching), and by how many centimeters on each side.
- Throw distance from the screen size: the screen size you enter is used as the target screen, so the image and the screen match and there is no margin or overflow.
- Image width from the throw distance: the screen size is optional. If it is empty, the image is not compared with a screen and only its size is shown. The screen you enter is assumed to have the same aspect ratio as the image.
Zoom lens display
When the throw ratio has a range (minimum to maximum), the drawing overlays two spreads and two images.
- Throw distance from the screen size: the lower throw ratio is the "shortest throw distance" (solid) and the higher ratio is the "longest throw distance" (dashed). They show the same screen filled from a nearer and a farther position.
- Image width from the throw distance: at the same distance, the lower throw ratio gives the "largest image" (wider; dashed) and the higher ratio gives the "smallest image" (narrower; solid).
Assumptions in the drawings
- The center of the image and the center of the screen are drawn as aligned. A real projector may place the image higher, lower or to the side (a vertical offset built into the lens design, lens shift and so on). The throw ratio alone does not determine this, so the drawings do not reproduce it.
- Keystone correction, the shape of the screen and the angle of installation are not reflected.
- The top view shows the horizontal direction only.
- Distances in the drawings are in meters. Feet and centimeters are shown in the results.
- For a real installation, check the manufacturer's lens specifications and the throw distance table in the manual.
What the throw ratio is
The throw ratio is the distance from the projector to the screen (the throw distance) divided by the width of the image.
- Throw ratio = throw distance ÷ image width
- Throw distance = image width × throw ratio
- Image width = throw distance ÷ throw ratio
The lower the throw ratio, the larger the image you can get from a short distance (a short-throw projector). A zoom lens has a range of throw ratios (for example 1.2 to 1.5), so you can adjust the image size without moving the projector.
This tool always uses throw distance ÷ image width. Some manufacturers quote the ratio against another size, such as the diagonal. Make sure the value you enter is based on the image width.
How to measure the throw distance
- The throw distance is normally measured from the lens reference point to the screen, not from the front or back of the projector. The reference point differs between models.
- Check the manufacturer's lens specifications and the throw distance table (the table of image sizes and distances in the manual). The result here is an estimate from the throw ratio.
- Lens shift, keystone correction and the effect of the screen's shape or angle are not included.
Examples
- Image width 2 m, throw ratio 1.5 (fixed lens): throw distance 3 m (9.84 ft).
- 100 in, 16:9 (image width about 2.214 m), throw ratio 1.2 to 1.5 (zoom): throw distance about 2.657 to 3.321 m (8.72 to 10.89 ft).
- Throw distance 3 m, throw ratio 1.2 to 1.5 (zoom): image width 2 to 2.5 m.
Notes
- The image width and the distance can be entered in inches, cm, mm, m or feet (1 in = 25.4 mm). The throw ratio must be greater than 0 and at most 100, and can have decimals. Use a period as the decimal separator; commas are accepted only as thousands separators.
- For a zoom lens, the maximum throw ratio must be at least the minimum.
- When you give the screen size as a diagonal, check that it is the length of the picture's diagonal, without the frame or bezel. To convert between a diagonal and a width and height, use the Screen Size Calculator.
- To work out an aspect ratio, use the Aspect Ratio Calculator.
- The margin and overflow in the drawing assume the image and the screen are centered on each other.
Frequently asked questions
How far should I place the projector for a 2 m wide image at a throw ratio of 1.5?
2 × 1.5 = 3 m, measured from the lens reference point to the screen.
What does a throw ratio of 1.2 to 1.5 mean for a zoom lens?
For the same image width, you can place the projector anywhere from 1.2 to 1.5 times the width away. If the distance is fixed, you can adjust the image size with the zoom.
Can I measure from the front of the projector?
Normally you measure from the lens reference point, which differs between models. Check the manual or the throw distance table.
What should I check before installing?
The throw ratio (minimum and maximum) and the throw distance table in the manufacturer's specifications. If you use lens shift or keystone correction, check their ranges too.