Tool21:9 Aspect Ratio Calculator
Calculate ultrawide dimensions with the exact 64:27 ratio, with presets for real 21:9 monitors.
Ratio is locked to the true ultrawide 64:27. Edit the width and the height updates automatically, or edit the height to solve for the width.
21:9 ultrawide resolution chart
| Name | Resolution | Use |
|---|---|---|
| UW-FHD | 2560 × 1080 | Entry ultrawide monitors |
| UW-QHD | 3440 × 1440 | Most popular ultrawide |
| — | 3840 × 1600 | High-detail productivity |
| UW-4K / DUHD | 5120 × 2160 | Premium ultrawide displays |
Where 21:9 is used
Ultrawide 21:9 is built for immersion and horizontal workspace: cinematic films (mastered near 2.39:1 fill the screen with no bars), racing and flight sims, and productivity setups where two or three documents sit side by side. It replaces a dual-monitor bezel with one continuous panel.
The math behind 21:9
"21:9" is a marketing label — the exact panel ratio is 64:27 (≈2.37:1). Height from a width is height = width × 27 ÷ 64; width from a height is width = height × 64 ÷ 27. That is why real panels land on numbers like 3440×1440 rather than a clean 21-to-9 division.
Related calculators
- Aspect Ratio Calculator — any custom ratio
- 16:9 Aspect Ratio Calculator — standard widescreen
- 4:3 Aspect Ratio Calculator — classic and tablet screens
- What Is My Screen Resolution — detect your display size
Frequently Asked Questions
What is the 21:9 aspect ratio in pixels?
Marketing calls it 21:9, but true ultrawide resolutions are usually 64:27. Common sizes are 2560×1080 (UW-FHD), 3440×1440 (UW-QHD) and 5120×2160 (UW-4K / DUHD). This calculator uses the exact ultrawide ratio so the presets match real monitors.
Is 3440×1440 a 21:9 monitor?
Yes — 3440×1440 is the most popular "21:9" ultrawide resolution. Its exact ratio is 43:18 (≈2.389:1), which manufacturers round to 21:9. Enter 3440 as the width above to see the matching height.
Why do 21:9 monitors sometimes show black bars?
Most video is mastered in 16:9, so a 16:9 clip on a 21:9 screen leaves black bars on the left and right. True cinematic content (often 2.39:1) fills a 21:9 display almost edge to edge, which is why films look great on ultrawide.
How do I calculate a 21:9 height from a width?
Ultrawide uses the ratio 64:27, so height = width × 27 ÷ 64. A width of 3440 gives 3440 × 27 ÷ 64 ≈ 1451, which manufacturers round to 1440 for the panel. Enter any width above for the exact ultrawide height.