Aspect Ratio Converter
Convert between diagonal, width and height, and see how much space content of each ratio really takes
Image width = diagonal × ratio width ÷ √(width² + height²). For a 100-inch screen: a 16:9 image is 2.21 × 1.25 m, 4:3 is 2.03 × 1.52 m and 21:9 is 2.33 × 1.00 m. The same "100 inches" gives very different width and height at different ratios — always check against the clear wall width before ordering, not just the diagonal.
Size conversion
Result
Actual displayed size for different content ratios
Treat the screen above as a frame; the table shows the area each content ratio occupies and the black bars it leaves.
| Content ratio | Displayed area (width × height) | Black bars |
|---|
Width and height for the same diagonal at different ratios
"100 inches" is only a diagonal length; the actual width and height differ greatly with the ratio. The table below converts common diagonals.
| Diagonal | 16:9 | 4:3 | 21:9 |
|---|
FAQ
Why not use the shortcut “diagonal ÷ 5 × 4”?
That is a rough approximation for 16:9 (4/5 = 0.8), while the exact factor for 16:9 is 16 ÷ √(16²+9²) ≈ 0.8716, a difference of about 8.9%. For a 100-inch screen the approximation gives a width of 2.03 m against an actual 2.21 m — an 18 cm error that is enough to affect installation. These tools always use the exact formula.
What happens when 4:3 content is shown on a 16:9 screen?
The content fills the screen height and leaves a vertical black bar on each side. On a 100-inch 16:9 screen, 4:3 content occupies about 1.66 × 1.25 m with roughly 0.28 m on each side. Conversely, 21:9 content on a 16:9 screen leaves black bars top and bottom.
When buying a screen, should I check the width or the diagonal?
Check the width. Wall width is a hard constraint, whereas the diagonal is derived. Screens with the same diagonal but different aspect ratios can differ in width by more than ten centimeters. Confirm the usable clear wall width first, then work back to an acceptable diagonal.
Must the projector's native aspect ratio match the screen's?
They do not have to match exactly, but a mismatch produces black bars or image scaling. A common approach is to match the screen to your main source content (most home content is 16:9) and accept black bars for other aspect ratios rather than stretching the image.