21:9 Aspect Ratio Calculator + Bulk Resizer
Work out any 21:9 ultrawide dimension, then resize or crop a whole folder of images to match — free, in your browser.
Work out any 21:9 ultrawide dimension, then resize or crop a whole folder of images to match — free, in your browser.
The 21:9 aspect ratio is the ultrawide format used by cinematic film and ultrawide monitors. The name is marketing shorthand — real ultrawide panels are typically 64:27 (2.37:1) or 43:18, not exactly 21:9. It is close enough that everyone calls it 21:9, and close enough that content authored for one fits the other with a sliver of letterboxing.
| Resolution | Name | Category | Megapixels | Resize to this size |
|---|---|---|---|---|
| 2560x1080 | UWFHD Monitor | Screen | 2.8 MP | Resize to this — 2560 by 1080 pixels, UWFHD Monitor |
| 3440x1440 | UWQHD Monitor | Screen | 5.0 MP | Resize to this — 3440 by 1440 pixels, UWQHD Monitor |
| 5120x2160 | 5K2K Ultrawide | Screen | 11.1 MP | Resize to this — 5120 by 2160 pixels, 5K2K Ultrawide |
| 2560x1097 | Cinematic 2.35:1 | Video | 2.8 MP | Resize to this — 2560 by 1097 pixels, Cinematic 2.35:1 |
| 3840x1646 | 4K Cinemascope | Video | 6.3 MP | Resize to this — 3840 by 1646 pixels, 4K Cinemascope |
| 1920x823 | Cinematic 1080p | Video | 1.6 MP | Resize to this — 1920 by 823 pixels, Cinematic 1080p |
| 2100x900 | Web Banner | Screen | 1.9 MP | Resize to this — 2100 by 900 pixels, Web Banner |
| 6720x2880 | 6K Ultrawide Master | Video | 19.4 MP | Resize to this — 6720 by 2880 pixels, 6K Ultrawide Master |
Wallpapers and dashboards for 34" and 49" ultrawide displays
The letterboxed look of theatrical film, roughly 2.35:1
Ultrawide gaming at 3440x1440 is the enthusiast standard
Hero images and site headers that need to span a full viewport
Not exactly. 3440x1440 simplifies to 43:18, which is 2.389:1 — slightly wider than a true 21:9 (2.333:1). Manufacturers round it to 21:9 for marketing. The difference is small enough that you will only notice it as a thin bar when playing true 21:9 content.
21:9 is 2.33:1, and cinematic Cinemascope is usually 2.35:1 or 2.39:1. They are close cousins. Film shot at 2.39:1 shown on a 21:9 monitor leaves a barely visible letterbox, which is why ultrawide panels are marketed at movie watchers.
You cut the top and bottom — about 24% of the height disappears. That is a lot, and it is why cinematic crops of ordinary photos so often decapitate the subject. Check the batch afterwards rather than trusting a center crop.
Match your panel: 2560x1080 for UWFHD, 3440x1440 for UWQHD, 5120x2160 for 5K2K. Supplying a larger file is fine — the OS downsamples cleanly. Supplying a smaller one and letting it stretch is what makes wallpapers look soft.
A handful of phones offer a 21:9 cinematic mode, but it is a crop of a wider sensor rather than a native shape. If you want 21:9 stills, shoot the full sensor and crop afterwards — you keep the option to reframe.