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Aspect Ratio Calculator
Scaling only one side stretches a picture. Enter the original width and height, then fill in either the new width or the new height, and the tool returns the matching dimension plus the simplified ratio.
How to use it
- Enter the original width and height.
- Fill in the new width, or the new height — not both.
- Read the missing dimension and the simplified ratio.
Examples
- 1920 × 1080 is 16:9; at 1280 wide the height must be 720.
- 4000 × 3000 is 4:3; capped at 800 tall gives 1066.67 wide.
- A 1:1 crop for social: any square size keeps the ratio at 1:1.
Questions people ask
What are the common ratios?
16:9 for video and most screens, 4:3 for older displays and many cameras, 1:1 for square social posts, 9:16 for vertical stories and reels, and 21:9 for ultrawide monitors and cinematic footage.
Why do I get a fractional pixel?
Because the exact proportion does not land on a whole number. Round to the nearest pixel; a difference of half a pixel is invisible and will not noticeably distort the image.
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Updated: 2026-08-07