Free tool
Aspect ratio calculator
Overview
Enter a width and height to see the ratio, then resize to a new width or height and keep the shape.
Printable pack · $9
Ratio and Proportion Worksheet Pack
About fifty original problems on printable pages, from writing a ratio to word problems, with every answer worked out in a separate key.
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How it works
How it works
Divide both numbers by their greatest common divisor to get the simplest ratio. 1920 x 1080 divides by 120 to give 16:9. To resize, new height = new width x height / width, and new width = new height x width / height.
Example: a 1920 x 1080 image has a ratio of 16:9. To place it at a width of 1280, the height is 1280 x 1080 / 1920 = 720, so the new size is 1280 x 720 and the shape is unchanged. A 4000 x 3000 photo is 4:3, so a width of 800 needs a height of 600.
FAQ
About this calculator
What is an aspect ratio?
The proportion between width and height, written as width:height. A 16:9 screen is 16 units wide for every 9 units tall.
Why does my image look stretched after resizing?
The width and height were changed by different amounts. Change one, then calculate the other from the ratio so both scale together.
What if my size does not reduce to a common ratio?
Many camera and phone sizes reduce to an awkward ratio. The decimal width divided by height still lets you compare it with a standard shape such as 16:9 or 4:3.
Do the units matter?
No. Pixels, inches and centimeters all work as long as width and height use the same unit.
Is anything saved?
No. The math runs in your browser and nothing you enter is sent to us.
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Document pack
Ratio and Proportion Worksheet Pack
About fifty original problems on printable pages, from writing a ratio to word problems, with every answer worked out in a separate key.