Aspect Ratio Tester
Test and identify your display's aspect ratio. Run the browser-based check and follow its prompts to review the result.
Set these fields to preview a target shape, such as 16:9 or 4:3. They resize the frame above only; the viewport ratio shown earlier is measured from your current browser window.
Tool guide
About Aspect Ratio Tester
Compare your current browser viewport's width-to-height ratio with common display ratios and preview a target frame such as 16:9 or 4:3. The page measures the browser viewport, not the full physical monitor or an image file.
How to use this tool
- 1Resize the browser window to the area you want to inspect; the viewport measurements update in the tool.
- 2Read the measured ratio, nearest common ratio, and simplified pixel ratio.
- 3Change target width and height values to preview a frame shape. The preview does not resize the browser itself.
How the tool works
The viewport ratio is width divided by height. The tool finds the greatest common divisor of the current viewport dimensions to display a simplified pixel ratio, then compares the decimal ratio with a list of common formats. The target frame uses the CSS aspect-ratio property with the two entered numbers.
Worked real-world example
A viewport measuring 1440 by 900 has a ratio of 1.6:1, commonly written as 16:10. A target set to 16 and 9 previews a wider frame.
Common scenarios and use cases
Check responsive layouts, compare browser viewport shapes, and preview an aspect ratio for a media container.
Important details and limitations
Browser zoom, device pixel ratio, browser chrome, and resizing affect measurements. The viewport ratio is not necessarily the physical screen ratio. A nearest common match is only a comparison, not an exact classification of the display.
Check the output unit as well as the number. If the result will be reused in another calculation, retain full precision where possible and round only at the end. For measurements governed by a technical specification, use the standard and tolerance required by that document.
Frequently asked questions
Does it measure my whole monitor?
No. The ratio is based on the browser page viewport.
What does simplified pixels show?
It reduces the current viewport width and height by their greatest common divisor.
Does the target frame change my page size?
No. It only displays a preview frame inside the tool.