Where the 21:9 aspect ratio is used
21:9 is the marketing name for ultrawide monitors and the digital stand-in for 2.35:1 and 2.39:1 cinema. Real panels vary: 2560 × 1080 is about 2.37:1 and 3440 × 1440 about 2.39:1. 7:3 is the same shape as 21:9.
- Cinematic video: Close to the 2.35:1 and 2.39:1 theatrical film formats.
- Ultrawide monitors: The standard shape of single wide desk displays.
- Immersive gaming: PC games that use the extra horizontal field of view.
- Productivity: Two windows side by side on one screen.
21:9 resolution cheat sheet
| Name | Width × height | Typical use |
|---|---|---|
| UW-FHD (sold as 21:9) | 2560 × 1080 px | Entry-level ultrawide monitors |
| Exact 21:9 at 1080 tall | 2520 × 1080 px | Mathematically exact 21:9 export |
| UW-QHD (sold as 21:9) | 3440 × 1440 px | The popular ultrawide gaming resolution |
| UW-QHD+ (sold as 21:9) | 3840 × 1600 px | Premium productivity ultrawides |
| 5K2K ultrawide | 5120 × 2160 px | Top-tier editing monitors |
Tip: Edit at your monitor's real resolution, such as 3440 × 1440, so cinematic video fills an ultrawide screen without black bars.
How to calculate 21:9 dimensions
Height = width × 9 ÷ 21. Width = height × 21 ÷ 9. Round to whole pixels; many video encoders also need even numbers.
CSS for a 21:9 box
.media { aspect-ratio: 21 / 9; width: 100%; }