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Calculate aspect ratio and missing dimensions

Reduce width and height to their simplest ratio, or start with a target ratio and one known side to solve the other. The arithmetic stays in this browser tab.

Dimensions to aspect ratio

Reduce two whole-pixel dimensions to their simplest ratio and get a decimal, orientation, and CSS-ready values.

Simplified ratio

Enter width and height, then calculate. Both dimensions are divided by their greatest common divisor.

Ratio to missing pixel dimension

Choose a ratio and one known side. The other side is rounded to the nearest whole pixel when the proportion is fractional.

This calculator assumes square pixels. It does not crop or resize a file, guarantee a platform specification, or account for anamorphic pixel aspect ratios. Changing an existing asset to a different ratio still requires a crop, padding, or distortion decision.

How it works

01

Enter dimensions or a ratio

Type whole-pixel width and height values, or choose a ratio and one known pixel dimension.

02

Calculate the proportion

Simplify dimensions by greatest common divisor or solve the missing side with transparent whole-pixel rounding.

03

Copy the result

Copy the ratio, dimensions, decimal, orientation, and CSS-ready values without uploading a file.

What stays private here

  • No image or other file is selected, decoded, or uploaded.
  • Dimension arithmetic runs only in this browser tab.
  • No clipboard text or free-form content is sent to Peelaway.
  • Analytics receive only aggregate numeric dimensions, operation, and experiment attribution.

Questions about this tool

How is an aspect ratio simplified?

The calculator finds the greatest common divisor of width and height and divides both by it. For example, 1920×1080 reduces by 120 to 16:9.

How is a missing dimension calculated?

For a known width, multiply it by ratio height divided by ratio width. For a known height, multiply by ratio width divided by ratio height. Fractional results are shown and rounded to the nearest whole pixel.

Does this resize or crop an image?

No. It performs manual dimension arithmetic only. Changing a real asset to a different ratio still requires cropping, padding, or stretching in an image or video tool.

Are my dimensions stored or uploaded?

No file is selected. Calculations and copied summaries stay in this browser tab; analytics receive only aggregate numeric dimensions, operation, and experiment attribution.

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