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21:9 Aspect Ratio Calculator
Work with the 21:9 aspect ratio: enter one dimension and get the other keeping 21:9, or check whether a size matches 21:9. For example 2520 × 1080 is a 21:9 size (21:9 means 21 units wide for every 9 tall). The calculator reduces any width×height to its simplest ratio with the greatest common divisor and solves the missing dimension so images and video keep 21:9 without distortion — all in your browser. Common for ultrawide monitors and cinematic video.
21:9 means 21 wide for every 9 tall
- Example 21:9 size: 2520 × 1080
- Reduced via gcd; resize keeps the ratio (no distortion)
Frequently asked questions
What dimensions are 21:9?
Any width×height that reduces to 21:9. For example 2520 × 1080 is 21:9. Enter one dimension in the calculator and it returns the other keeping 21:9.
How do I resize to 21:9?
Set the ratio to 21:9, type your new width (or height), and the calculator computes the matching height (or width) so the image keeps 21:9 without stretching.