Created by Katakata · Last reviewed
How to use Aspect Ratio Calculator
Use this calculator when an image, video, embed, or CSS box must keep the same proportions at a new size. Enter a ratio and either width or height; the missing dimension is calculated immediately and the preview helps catch an accidental portrait or landscape orientation.
Practical workflow
- Enter the ratio as two positive values, such as 16 and 9, or use detection when you already know both pixel dimensions.
- Enter either the target width or height. The paired dimension updates from the exact ratio and is rounded for practical pixel output.
- Swap orientation when moving between landscape and portrait, then verify the receiving platform does not apply an additional crop.
Accuracy and limitations
A matching ratio does not guarantee that text or faces remain visible after a platform crop. The displayed pixel value is a geometric calculation, not a compression or image-quality estimate. For CSS layouts, consider using the native aspect-ratio property and allow the container width to remain responsive.
Privacy and data handling
All numbers are calculated locally. No dimensions or project data are transmitted to KatakataLab.
Why this page exists
KatakataLab publishes small browser tools built from recurring design and development tasks. This English page is maintained as a complete entry point, not as an automatic translation or a doorway page. If a control, explanation, or result is unclear, use the contact page and include the tool name, browser, and expected result without sending confidential input.
For another workflow, browse the English tool index or switch to the Japanese version.