Aspect Ratio Calculator
Enter a known width or height plus an aspect ratio to calculate the matching missing dimension, or enter two dimensions to find their simplified aspect ratio — handy for resizing images or video without distortion.
Calculators Runs entirely in your browser
All calculations happen on your device — nothing is sent to a server.
- Simplified ratio
- 16 : 9
What this tool does
Finds the missing dimension that preserves a given aspect ratio, and reduces a ratio to its simplest form, with presets for the common ones.
When to use it
- Changing an image or video's width and needing the height that keeps the ratio.
- Preparing content for a platform that requires a specific ratio.
- Finding a file's aspect ratio from its dimensions.
- Designing a frame or container at a fixed ratio.
How to use it
- Pick from "Common presets" or enter the "Ratio (width)" and "Ratio (height)".
- Enter whichever of "Width" or "Height" you know.
- Read the other dimension and the "Simplified ratio".
A practical example
Input
A 16:9 ratio with a width of 1280.
Output
A height of 720, and a simplified ratio of 16:9.
Limitations
- Ratio values must be greater than zero, and you get a clear message if they are not.
- Results can be fractional; for images and video you will need to round to whole pixels.
- Changing existing content's ratio means cropping or padding — the calculator gives you the numbers and does not perform the change.
Privacy and processing
The ratio arithmetic runs on your device and no dimensions are sent anywhere.
Technical notes
- Simplification uses the greatest common divisor, so 1920×1080 reports as 16:9 rather than 1920:1080.