Projector Throw Distance Explained: How Far Back Should Your Projector Sit?
Throw distance is the distance from the projector’s lens to the screen — and it is the one number that decides whether a projector works in your room at all. Put the projector too close and the image won’t fill the screen; too far and it overflows. This guide explains the simple math behind it, with a popular home projector as the worked example.
The throw ratio: the only spec that matters here
Every projector lens has a throw ratio, written like 1.02–1.23. It links image width to distance:
Throw distance = image width × throw ratio
Note it is the image width, not the diagonal you buy the screen by. For a 16:9 screen, width = diagonal × 0.872 (a 120″ screen throws a picture 104.6″ wide — see our screen size guide for the full chart).
Why two numbers? Most home projectors have a zoom lens. The first number is the closest the projector can sit (widest zoom), the second is the farthest (most telephoto). Anywhere inside that range, you can fine-tune the image size with the zoom ring instead of moving the mount.
Worked example: Epson Home Cinema 1080
The Home Cinema 1080 is one of Epson’s most popular home models, with a throw ratio of 1.02–1.23. Running the formula:
| Screen size (16:9) | Image width | Throw distance |
|---|---|---|
| 100″ | 87.2″ (7.3 ft) | 7.4 – 8.9 ft |
| 120″ | 104.6″ (8.7 ft) | 8.9 – 10.7 ft |
| 150″ | 130.7″ (10.9 ft) | 11.1 – 13.4 ft |
So in a typical living room with the projector ceiling-mounted or on a shelf 10 feet from the wall, this projector pairs naturally with a 120″ screen. Want the 150″ instead? You would need to get the lens 11.1 to 13.4 feet back — possible in a long room, impossible in many condos.
Projectors vary enormously. A longer-throw model like Epson’s Home Cinema 3800 (1.32–2.15) needs 11.5 – 18.7 ft for that same 120″ picture, while short-throw models do it from a few feet — we cover those in our short-throw guide.
How to measure your room
- Measure from the screen wall to where the lens will be — the front of the projector, not the back of the cabinet or the middle of the ceiling mount. On a ceiling mount, allow a few inches behind the lens position for the projector body and cables.
- Check the range, not a single number. Your mounting point has to fall inside the projector’s distance range for your screen size, ideally not at either extreme — mid-zoom usually gives you the most adjustment room during setup.
- Then pick the screen. If your distance is fixed by the room, work backwards: distance ÷ throw ratio = the image width you can fill, and from width to the matching screen size.
Skip the math
Our free Calculateur de distance de projection already holds the throw ratios for dozens of current models. Pick your projector, enter a screen size (or the distance you have), and it returns the exact distance range — plus the screens we carry in that size, from motorized and fixed frame to manual and portable.
