Aspect Ratio Calculator
Reduce any width and height to its simplest ratio, or work out the missing side for a target ratio such as 16:9, 9:16 or 4:5. Useful for video exports, thumbnails and responsive layouts.
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How to use the Aspect Ratio Calculator
- Enter a width and a height to see the simplified ratio and the nearest common ratio.
- To find a missing side, choose a ratio or type your own, then enter the side you know.
- Copy the result or use it in the Image Resizer.
Example
1920 × 1080 Target 9:16 with height 1920
Ratio 16:9 (1.7778) Width for 9:16 at 1920 high: 1080 px
About this tool
A ratio is width divided by height, reduced to whole numbers with the greatest common divisor. 1920 × 1080 and 1280 × 720 are both 16:9, which is why they scale into each other without distortion.
To find a missing side, multiply the known side by the other part of the ratio and divide by its own part. At 16:9, a 1280-pixel width needs 1280 × 9 ÷ 16 = 720 pixels of height.
Known limitations
- Results are rounded to whole pixels, so converting back and forth can differ by one pixel.
- Some screen sizes, such as 1366 × 768, do not reduce to a common ratio. The tool shows the exact ratio and the nearest common one.
Frequently asked questions
What ratio is 1080 × 1350?
4:5, a portrait ratio often used for feed posts.
What is the difference between 16:9 and 9:16?
The same shape rotated. 16:9 is landscape, 9:16 is portrait, the format of vertical short-form video.
Can I enter decimals such as 2.39:1?
Yes. Decimal ratios are accepted in the custom ratio fields and in width and height.