About the Aspect Ratio Calculator
Calculate 16:9, 4:3 and Other Aspect Ratios — Find the ratio of a width and height, then calculate matching dimensions for resizing videos, slides, presentations and photos.
Formula or method
The aspect ratio is width divided by height. Reduce whole-number dimensions by their greatest common divisor, then multiply or divide using the original ratio.
Worked example
1920 × 1080 simplifies to 16:9. A corresponding width of 1280 requires a height of 720.
How to use the tool
- Enter original width and height.
- Enter a proposed new width or height.
- Use the matching dimension to avoid stretching.
Common uses
YouTube thumbnails, slide decks, responsive images.
Assumptions and limitations
Best suited to whole-pixel dimensions. Resizing to calculated dimensions does not prevent cropping when the source and target ratios differ.
Frequently asked questions
What is the aspect ratio of 1080 × 1920?
It is 9:16, common for vertical videos and mobile stories.
Privacy and support
Your inputs are processed locally in your browser. ToolMosaic does not upload or store the values you enter in this tool. Our tools are free, and we appreciate your support.