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Arithmetic
Aspect ratio calculator
No file needed. Type what you know and it fills in the rest, so you can resize something without squashing it.
Change any field and the others follow.
Result
Why the numbers matter
Resizing an image to dimensions that do not match its original ratio stretches it. Faces get wider, circles become ovals, and the result looks subtly wrong in a way most people notice without being able to say why. If you need a specific shape, the honest options are to crop or to pad, never to stretch.
The simplest-form line below reduces any pair of numbers to its lowest terms, which is how you find out that 1512 by 1008 is really just 3:2.
Common questions
What ratio should a YouTube thumbnail be?
16:9, and 1280 by 720 is the usual size. Vertical short-form video is 9:16.
My photo is 4:3 and I need 16:9. What do I do?
Either crop the top and bottom with the crop tool, which loses content, or add bars with add a border, which keeps everything. Do not stretch it.
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