A 100-inch 16:9 picture needs about 2.66 m from lens to screen at a 1.2:1 throw ratio. At the same ratio, 80 inches needs about 2.13 m and 120 inches about 3.19 m. These are calculated optical distances, not the required room length: leave additional space for the projector body, cables and ventilation. The right distance depends on the exact model, not simply on whether the projector is described as portable, laser or 4K.
This guide is for planning a Hong Kong bedroom or living room. The tables use 16:9 geometry and documented throw-ratio references; they are not Elechid room tests or installation guarantees.
80, 100 and 120 inches: how much wall space?
The advertised inch size is the diagonal, not the width. A 100-inch 16:9 picture is about 2.21 m wide and 1.25 m high. Check the visible image area separately from the screen's frame, housing and mounting clearance.
| Diagonal | Image width | Image height |
|---|---|---|
| 80 inches | 1.77 m | 1.00 m |
| 100 inches | 2.21 m | 1.25 m |
| 120 inches | 2.66 m | 1.49 m |
Throw-distance table: measure from the lens
Lens-to-screen distance = image width × throw ratio. BenQ defines throw distance from the projector lens to the screen surface and throw ratio as distance divided by image width. Use the unrounded width when calculating, then round the result for planning.
| Diagonal | 1.17:1 ratio | 1.2:1 ratio | 1.5:1 ratio |
|---|---|---|---|
| 80 inches | 2.07 m | 2.13 m | 2.66 m |
| 100 inches | 2.59 m | 2.66 m | 3.32 m |
| 120 inches | 3.11 m | 3.19 m | 3.98 m |
These ratios are examples, not universal projector categories. If a model has an optical zoom range, use its documented minimum and maximum throw ratios. A fixed-ratio lens does not gain optical zoom because the menu offers digital resizing. Confirm the model's supported image-size range and manual before relying on a calculated distance.
Which listed models use these references?
- Yaber L2 placement information: this Elechid listing states 1.17:1. On that basis, 100 inches is approximately 2.59 m. Confirm the supplied Hong Kong edition's manual; do not substitute L2 Plus or another L2-series model's specifications.
- Yaber K3 Pro native 1080p and setup requirements: Yaber publishes 1.2:1 for the K3 series. Check the exact bundle and installation chart.
- Kodak Luma 350 resolution and dark-room requirements: the official reference is 1.2:1. The same calculated distance does not mean the same sharpness or brightness as another model; its native resolution is 854 × 480.
- NexiGo Nova Mini placement and USB-C power requirements: the Elechid listing uses 1.2:1. Confirm the supplied manual and external power arrangement.
Two hypothetical Hong Kong room examples
A bedroom with only 2.2 m of usable optical distance
At 1.2:1, the calculated full image width is 2.2 ÷ 1.2 = 1.83 m, equivalent to approximately 83 inches at 16:9. An 80-inch plan may fit the optical path, but a 100-inch full image would need about 2.66 m. This example starts with lens-to-screen distance after clearance has been allowed, not a 2.2 m wall-to-wall room measurement.
A living room aiming for 120 inches
At 1.2:1, allow approximately 3.19 m from lens to screen and a visible image about 2.66 m wide. If a sofa, rear shelf, light fitting or walkway obstructs that path, increasing the advertised brightness does not solve the geometry. A smaller picture, different position or suitable shorter-throw model may be more practical.
Why ultra-short-throw needs its own diagram
Ultra-short-throw projectors use a different installation geometry. A quoted lens-to-screen distance is not necessarily the gap between the rear of the case and the wall. Follow the exact model's diagram for cabinet depth, case position, screen height and image offset. A compatible UST/CLR screen also has directional requirements. Read the white wall, ALR and CLR screen guide before ordering.
Measure these six things before buying
- Clear wall or screen image width and height, excluding frames and furniture.
- Usable lens-to-screen distance at the intended projector position.
- Body depth, cable bend space and ventilation clearance required by the manual.
- Lens height, image offset and any mounting constraints.
- Room light, curtains and screen type; a distance calculation does not prove daytime performance.
- Power, HDMI or network routes and the supported apps you actually want to use.
For ceiling mounting or a heavy screen, have a qualified installer assess the fixing surface and use approved hardware. Automatic keystone correction cannot make an unsafe or obstructed installation suitable.
Frequently asked questions
Is viewing distance the same as throw distance?
No. Viewing distance is where you sit; throw distance is the optical path from lens to screen. A sofa can be closer than the projector, but the projector still needs its required path.
Can digital zoom make 100 inches fit a shorter distance?
Digital shrinking can reduce an existing image, but it cannot create a physically larger full image at a distance the lens does not support. It can also reduce the useful pixel area. Optical zoom, where provided, must be assessed using the specified lens range.
Does keystone correction replace proper placement?
No. It digitally reshapes the image and may reduce useful detail or leave unused borders. Start with physical alignment and the correct throw distance rather than choosing a heavily angled position first.
Can I project onto the ceiling?
Only if the exact model and mounting arrangement permit it. Check tilt limits, ventilation and safe support. A rotating stand does not automatically authorise every orientation.
Related guides and models
- Choose a projector by room and use
- Native resolution and brightness buying guide
- TV or projector for a small Hong Kong flat?
- Browse projectors and installation accessories
Sources and calculation notes
Prepared by the Elechid editorial team. Source check: 8 October 2026. Distances are calculations using diagonal × 0.0254 × 16 ÷ √337 × throw ratio; height uses 9 instead of 16. They are not measured results. Recheck manufacturer documentation for your supplied edition before purchase or installation.
