Aspect Ratio Simplifier

Reduce dimensions to a width:height ratio, resize while preserving that ratio, and process batches locally in the browser.

Last reviewed: June 2026
Reviewed by , software engineer · last updated June 2026

New to this tool? Click here for instructions

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16:9
Common Ratio Reference
RatioDecimalCommon UsesExample Resolutions
Enter width and height in pixels to calculate the aspect ratio.

How to use the Aspect Ratio Simplifier

Enter integer width and height values in Single mode to get the reduced ratio, greatest common divisor, decimal value, and a scaled preview box. Use Resize Calculator mode when one dimension is fixed and you need the matching width or height. Use Batch Mode for one dimension pair per line, such as 1920x1080 or 1080 1920.

All calculations run locally. The tool only needs the numeric dimensions you enter; it does not upload images, inspect files, or infer an image's natural dimensions.

How the math works

The tool applies the Euclidean greatest common divisor algorithm. If the width is 1920 and the height is 1080, the GCD is 120. Dividing both dimensions by 120 gives 16:9. If the width is 1080 and the height is 1920, the same process gives 9:16, because orientation matters.

In resize mode, the formula is proportional scaling: new height = new width x original height / original width, or new width = new height x original width / original height. The displayed value is rounded to the nearest whole pixel because CSS and image exports usually need integer dimensions.

Practical workflows

Responsive images: reduce source dimensions before setting CSS aspect-ratio or reserving layout space for images and videos.

Video and thumbnails: compare 16:9, 9:16, 4:3, 1:1, and 21:9 outputs before creating crops for different platforms.

Batch audits: paste several image or canvas dimensions to find out which assets are true 16:9, which are vertical 9:16, and which have unusual ratios that may need custom handling.

Tips and limitations

  • A ratio is not a fixed resolution. 16:9 can be 1280x720, 1920x1080, 2560x1440, or any other dimensions with the same proportion.
  • Fractional or physical units should be converted to integers before use; the browser inputs are intended for pixel-like dimensions.
  • Very close dimensions can reduce to uncommon ratios. That is not an error; it usually means the source asset has been cropped, rounded, or padded.
  • CSS aspect-ratio works with a preferred width-to-height ratio, but fixed width and fixed height together can still override the effect.

Useful reference: MDN CSS aspect-ratio.

Frequently Asked Questions

Aspect ratio is the proportional relationship between width and height, expressed as width:height.
The tool divides both dimensions by their greatest common divisor. For 1920x1080, GCD 120 gives 16:9.
16:9 is not one pixel size. Common 16:9 resolutions include 1280x720, 1920x1080, 2560x1440, and 3840x2160.
1080x1920 reduces to 9:16, which is the vertical orientation of the 16:9 family.
No. Single, resize, and batch calculations run locally in the browser.