Aspect Ratio Calculator
Enter a width and height to get the ratio — and resize to any target without distortion.
How to use
- Enter the original width and height in pixels (or any unit).
- Read the simplified aspect ratio — common standards like 16:9 or 4:5 are named.
- Type a target width or target height to get the matching other dimension for a distortion-free resize.
Examples
Resize a Full HD frame
1920 × 1080 is 16:9. A target width of 1280 gives a height of 720 — the image scales without stretching.
Instagram portrait crop
4:5 is the tallest feed format. For a 1080-pixel-wide post, the height is 1350.
FAQ
What is an aspect ratio?
The proportional relationship between width and height, written as width:height. A 1920×1080 image and a 1280×720 image are different sizes but the same 16:9 shape.
How is the missing dimension calculated?
By proportion: new height = new width × (original height ÷ original width), and the same the other way. This keeps the shape identical, so nothing looks stretched.
Why does 2560×1080 show as 64:27 and not 21:9?
21:9 is a marketing name — the true simplified ratio of most “21:9” ultrawide screens is 64:27 (≈2.37:1). The tool shows the exact ratio and notes that it is the ultrawide format.
Should the result be rounded to whole pixels?
Yes for images and video — the tool rounds targets to sensible precision, and a half-pixel difference is invisible. Keep exact values only for print or vector work.