Projector Screen Throw Distance Ratio Tool
Visual placement planner
- Screen
- 120 in · 16:9
- Lens-to-screen distance
- 12 ft
Lens placement range
- Minimum
- 10.46 ft
- Maximum
- 13.07 ft
Your position: 12 ftInside range
Minimum lens distance: 10.46 ft. Maximum lens distance: 13.07 ft. Your position: 12 ft. Inside range. Basic optical distance only; mounting verification is still required.
Fits — Basic Distance Check. 16:9 screen, 120 inches diagonal. Lens distance 12 ft. Placement range 10.46 to 13.07 ft. Mounting height and offset are not modeled.
Illustrative and not to scale. The side view does not establish mounting height, vertical offset or lens shift.
Compatible Projectors
No manufacturer-verified products are available. No projector is labeled compatible.
- Verify the exact lens, throw-ratio range, active image format and supported diagonal.
- Compare your required distance with the manufacturer’s placement table.
- Check lens shift, offset, mounting orientation, body size and ventilation.
Matching Screens
No verified screen catalog is available. No screen is labeled compatible.
- Match active image width, height and aspect ratio; allow space for the frame.
- Verify screen mounting and room obstructions.
- For ultra-short-throw setups, obtain explicit projector/screen pairing confirmation where required.
Shopping guidance only. No product prices or ratings are provided. General browsing links do not establish compatibility.
How to use
Find projector throw distance, screen size or required throw ratio. Check basic room fit and explore a visual placement planner.
Choose Throw Distance to plan a desired diagonal, Screen Size to discover the image range at an available distance, or Required Throw Ratio to work backward from your room and screen. Enter the active image aspect ratio and choose feet or meters. Unit changes convert entered distances; screen diagonals always use inches.
Use the exact lens specifications from your projector manual. Equal minimum and maximum ratios represent a fixed lens. In Required Throw Ratio mode, comparison is optional and uses only the range you confirm you verified. No manufacturer model is independently checked. Reset example restores 120 inches, 16:9, 1.2–1.5 and 12 feet.
Methodology and worked example
Methodology and formulas
Throw ratio compares lens distance with screen width. If diagonal is D and aspect dimensions are a:b, width = D × a / √(a² + b²) and height = D × b / √(a² + b²). Distance = width × throw ratio. Convert all lengths to the same unit before multiplying or dividing.
For a fixed distance, width = distance / throw ratio; diagonal = width × √(a² + b²) / a. Required ratio = distance / width. Minimum ratio gives minimum placement distance and maximum possible image width. Maximum ratio gives maximum distance and minimum width. Zoom ranges describe an optical placement interval, subject to the model’s supported image sizes and settings.
Worked example
The example 120-inch 16:9 screen is 104.59 inches wide and 58.83 inches high. A 1.2–1.5 ratio gives approximately 10.46–13.07 feet. A 12-foot lens distance passes the basic optical check; the required ratio is approximately 1.38. Mounting verification remains necessary. Arithmetic uses meters internally with 1 inch = 0.0254 meter and 1 foot = 0.3048 meter; rounding is for display only.
Measuring and planning placement
Measure horizontally from the manufacturer’s lens reference point to the active screen surface. Avoid measuring from the back of the chassis or from wall to wall. Include the screen frame, furniture, rear connectors and ventilation when assessing usable room space. A large diagonal can disguise how much width a widescreen image needs.
Standard throw generally places the projector farther away than short throw for the same image width. Ultra-short throw places it very near the screen using specialized optics. These labels do not replace an exact ratio and manufacturer placement table; this tool assigns no universal numeric class boundaries.
Common mistakes include using diagonal instead of width, reversing the zoom endpoints, mixing inches with feet, assuming every small image is supported, and treating a room-depth measurement as a lens distance. Test the intended format and optical zoom setting against the manual before fixing a mount.
Mounting and installation limitations
The fit state is limited to basic geometry. A passing distance never guarantees successful installation. Check vertical offset, horizontal and vertical lens shift, ceiling orientation, keystone restrictions, ventilation, structural mounting requirements and the complete projection path. No numeric offset, lens shift or mounting height is assumed.
The optional physical envelope adds lens distance, full body depth and additional front/rear allowances. It is conservative only for the stated front-lens reference-plane arrangement. Enter all three physical dimensions and room depth to compare. A failed room comparison produces Needs Mounting Verification; a known optical failure remains Doesn’t Fit — Throw Distance. Missing physical values do not establish clearance. For UST, recessed lenses or unusual housings, use model-specific drawings instead.
Guardrails are diagonal 1–1,000 inches, ratio 0.01–20, relative aspect dimensions 0.01–100, distance/room depth 0.01–300 selected units and body/allowances 0–30 selected units. These limits protect arithmetic and readability; they are not equipment specifications. Screen Size mode reports mathematical possibilities without certifying the model’s image-size limits. Values remain in browser memory and are not stored or transmitted by this calculator.
FAQ
What is projector throw ratio?
Throw ratio is lens-to-screen distance divided by active image width, using the same length unit. A ratio of 1.5 needs a distance 1.5 times the image width. It does not use the diagonal.
How far away should a projector be for a 120-inch screen?
At 16:9, a 120-inch diagonal is about 104.59 inches wide. A 1.2–1.5 throw-ratio range gives approximately 10.46–13.07 feet from lens to screen. Other lenses need different distances.
Does a basic fit mean installation is approved?
No. It checks optical distance against the entered range. Mounting height, lens shift, vertical offset, ventilation, obstructions and the screen pairing still require verification.
Why is the smallest screen calculated from the largest ratio?
At a fixed distance, image width equals distance divided by throw ratio. A larger denominator produces a smaller image. The diagonal and height follow the selected aspect ratio.
Can I enter a fixed lens?
Yes. Enter the same minimum and maximum throw ratio. The placement range becomes a single distance; the screen-size range also collapses to one size.
Can I use custom aspect ratios?
Yes. Select Custom dimensions and enter positive relative width and height from 0.01 to 100. Values such as 21 and 9 specify shape, not physical screen dimensions. Verify the projector supports that image format.
Is room depth the same as throw distance?
No. Measure from the specified lens reference point to the image surface. Body depth, rear cables, ventilation and obstructions can consume additional room space. The optional envelope is a conservative front-lens planning approximation.
Does this verify ultra-short-throw projectors?
No. UST equipment can use folded optics and model-specific reference points. Confirm the manufacturer’s placement drawing, mounting restrictions and explicit screen pairing where required. Generic side-view geometry cannot establish those details.
Will keystone correction fix a poor placement?
Do not rely on that assumption. Keystone limits, image cropping and usable resolution depend on the model and configuration. Verify permitted placement, offset and lens shift in the exact manual.
Are product recommendations or affiliate links active?
No. There are no verified projector or screen products in this release and no active affiliate links. Use the buying checklists to obtain exact specifications before purchasing.
Sources and review
Implementation reviewed locally October 17, 2026. Formulas are rectangular geometry and the definition of throw ratio. These manufacturer references illustrate why exact format, zoom and installation drawings matter; they are not preset data or approval of this calculator’s results. No independently verified product catalog is included.