Room planning tool
TV Viewing Distance Calculator
Compare calculated 40° and 30° viewing distances from the screen diagonal.
Find your viewing distance range
Use the 40° and 30° results as geometry examples, not universal seat rules.
Geometry and limits
This calculator assumes a centered viewer and a 16:9 visible image. It first calculates image width from the diagonal: width = diagonal × 16 ÷ √(16² + 9²). For a horizontal image angle θ in degrees, seat distance = width ÷ (2 × tan(θ × π ÷ 360)). The 40° and 30° outputs are geometry examples, not universal comfort recommendations.
For a 65-inch 16:9 screen, the examples are about 6.5 feet at 40° and 8.8 feet at 30°. Treat them as comparison points, not required seat marks. Test the proposed position with painter's tape on the wall, then account for reclining seats, off-center viewers and walkways.
Source checks, September 30, 2026: the THX Screen Placement FAQ URL returned HTTP 403 and could not be reviewed, so no THX recommendation is used here. SMPTE ST 2080-3:2017, section 5.3 describes reference-display viewer position, not total screen angle or home seat distance. The SMPTE EG-18 withdrawal notice documents that guide's withdrawal. The 40° and 30° values above are geometric calculations, not recommendations attributed to these sources.
For projector rooms, viewing distance does not determine lens placement. Confirm throw range separately in the home theater projector guide, then compare specific models in good projectors for home theater.
If you know the diagonal but need its physical wall size, use the screen size calculator.
Check the room before moving seats
- Measure from the screen plane to your eyes in the normal seated position.
- Test every main seat because side seats see a different effective angle.
- Keep doors, aisles and speaker positions clear at the chosen distance.
Viewing distance questions
Should I use the near or far result?
Compare the two example distances, then choose a seat that feels comfortable in your room. Test the position before fixing furniture.
Does the calculator work for projectors?
Yes. The viewing-angle math applies to the image, but projector throw distance still depends on the exact lens.
Why is the answer a range?
The two angles show how calculated seat distance changes as the horizontal image angle changes. They are comparison values, not one universal answer.