21:9 Aspect Ratio - Width, Height & CSS Dimensions
A 21:9 aspect ratio means width is 21 units for every 9 units of height. Ultrawide cinema and gaming monitors. At 2560px wide, the matching height is 1097px. Use the calculator below for any width or height.
Dimensions
Simplified ratio
2560:1097.1429
Common ratios
Social media
Photography
Common ratios
Social media
Photography
21:9 dimensions reference
Ultrawide cinema and gaming monitors. Sample calculation: 2560px × 1097px preserves 21:9. Adjust width in the tool above to regenerate height instantly.
21:9 Aspect Ratio FAQ
What is the 21:9 aspect ratio?
21:9 expresses width-to-height as 21:9. Ultrawide cinema and gaming monitors. In CSS, write aspect-ratio: 21 / 9. The decimal width÷height value is approximately 2.3333.
If width is 2560px at 21:9, what is the height?
Multiply width by 9/21: 2560 × (9 ÷ 21) = 1097px. Enter 2560 in the width field with ratio locked to 21:9 and the tool returns 1097px automatically.
What pixel dimensions are common for 21:9?
21:9 ultrawide content may target 2560×1080 or 3440×1440 px on cinema-wide monitors.
How do I set 21:9 in CSS?
Use aspect-ratio: 21 / 9 on a block container. Pair it with width: 100% or a fixed max-width; the browser computes height. For embedded video, wrap the iframe in a 21:9 box to prevent cumulative layout shift.
21:9 calculator vs generic resize tool: why use a ratio-specific page?
Ratio-specific pages document common resolutions and use cases for 21:9 without hunting presets. The embedded calculator is pre-loaded with 21:9 so you skip manual ratio entry - helpful when sharing links with teammates or clients.
Where is the full aspect ratio calculator?
The main Aspect Ratio Calculator supports any custom ratio, simplified GCD output, and all presets. Visit /dev-tools/aspect-ratio-calculator/ for the complete tool with methodology and cross-links to other Dev Tools.
Sources & review
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