About the Aspect Ratio Calculator
An aspect ratio calculator works out the ratio between a width and a height (for example 1920 × 1080 = 16:9) and helps you resize images, videos or screens without distortion. Enter a width and height to get the simplified ratio, and optionally a new width to find the matching new height.
How Aspect Ratio works
The aspect ratio is width : height reduced by their greatest common divisor (GCD).
Example: 1920 and 1080 share a GCD of 120, so 1920 ÷ 120 : 1080 ÷ 120 = 16 : 9. To resize, keep the ratio: new height = new width × height ÷ width.
Common uses
- Find the aspect ratio of a screen, image or video
- Resize an image to a new width without distortion
- Check common ratios like 16:9, 4:3 and 21:9
- Plan video or social-media dimensions
Frequently asked questions
How do I calculate aspect ratio?
Divide both width and height by their greatest common divisor. 1920 × 1080 becomes 16:9.
What is 16:9?
A widescreen ratio used by most TVs, monitors and HD/4K video — 16 units wide for every 9 tall.
How do I resize keeping the ratio?
Multiply the new width by the original height ÷ original width. This tool does it for you.