21:9 aspect ratio
The marketing name for ultrawide monitors and cinema-style video, close to the 2.39:1 of anamorphic film. 4 common sizes from 2560×1080 to 5120×2160, each shown with the exact ratio it reduces to.
Part of design tools and image tools.
Height
1097.14
21:9 resolutions
Each size below is shown with the ratio it actually reduces to, computed when this page was built.
| Resolution | Known as | Exact ratio | Copy |
|---|---|---|---|
| 2560×1080 | UW-FHD | 64:27 | |
| 3440×1440 | UW-QHD | 43:18 | |
| 3840×1600 | UW-QHD+ | 12:5 | |
| 5120×2160 | UW-5K (5K2K) | 64:27 |
No common screen is exactly 21:9 (2.33:1). Ultrawide sizes are built by widening a standard height, so they land on 64:27, 43:18 or 12:5 instead — all within 3% of 21:9, which is why the rounded name stuck. Use the exact ratio of your target size when cropping, or the edges will not line up.
Where 21:9 is used
ultrawide monitors · cinematic video · racing and flight games
The math
21:9 is 2.33:1: the width is 21/9 times the height. To get a height from a width, multiply by 9 and divide by 21 — 2560 × 9 ÷ 21 = 1097.14. Not the 1080 of the 2560×1080 in the table: that size is only close to 21:9. The calculator above does the same for any width or height, and gives the ratio of any size in the other mode.
Other aspect ratios
A little narrower: 16:9 (1.78:1).
Or open the aspect ratio calculator to work from any other ratio or size.