Aspect Ratio Calculator
Resize without distorting, or find out what ratio a size actually is.
In short
To resize while keeping proportions, divide the new width by the old width and multiply the height by the same factor. A 1920 by 1080 image scaled to 1280 wide becomes 1280 by 720, because both are 16:9. Changing only one dimension stretches the image.
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The rule
To resize without distorting, change both dimensions by the same factor:
new height = old height x (new width / old width)A 1920 by 1080 image scaled to 1280 wide becomes 1280 by 720, because both are 16:9. Change only one dimension and the image stretches, which is instantly visible on anything containing a face or a circle.
Finding the ratio of a size
Divide both numbers by their greatest common divisor. For 1920 by 1080 that is 120, giving 16:9. For 1440 by 960 it is 480, giving 3:2.
Some sizes do not reduce to anything recognisable. 1366 by 768, a very common laptop resolution, is 683:384, which is close to 16:9 but not exactly it. That small mismatch is why video on those screens sometimes shows a one-pixel band.
Which ratio to use where
| Ratio | Shape | Used for |
|---|---|---|
| 16:9 | Widescreen | Video, YouTube, presentations, most monitors and phones |
| 9:16 | Tall | Stories, Reels, TikTok, phone wallpapers |
| 1:1 | Square | Profile pictures, app icons, Instagram square posts |
| 4:5 | Portrait | Instagram portrait, the largest space in the feed |
| 4:3 | Classic | Older cameras, some projectors, iPad |
| 3:2 | Photographic | DSLR sensors, 6x4 inch prints |
| 21:9 | Ultrawide | Cinema, ultrawide monitors |
| 1.91:1 | Wide banner | Open Graph cards and link previews |
Why platforms crop your images
Every feed displays a fixed shape. Upload something a different shape and the platform trims the excess, usually from the centre outward, and usually without asking.
That is how faces end up cut in half in link previews and how the important part of a photo disappears. Cropping to the target ratio yourself before uploading means you decide what survives. The image cropper has presets for the common ones.
A related habit worth having: keep anything important away from the edges. Platforms change their display ratios periodically, and a composition that only just fits today gets clipped after the next redesign.
Ratio is not resolution
Two different things that get conflated constantly.
Ratio is the shape. 1280 by 720 and 1920 by 1080 are both 16:9.
Resolution is the pixel count, which determines how much detail there is and how large the image can be shown before it looks soft.
Matching the ratio stops distortion and cropping. Matching or exceeding the resolution stops softness. You usually want both, and you can always scale down without loss while scaling up never truly works.
Printing is a different problem
Standard print sizes are not standard ratios. A 6 by 4 inch print is 3:2, matching most camera sensors. But 5 by 7 is 7:5 and 8 by 10 is 5:4, so a photo straight from a camera will be cropped to fit either.
Which is why printed photos often lose a little from the sides that looked fine on screen. If you know the print size in advance, crop to that ratio first.
Frequently asked questions
How do I resize an image without distorting it?
Change both dimensions by the same factor. If you halve the width, halve the height. Enter your original size and one new dimension, and the other is filled in so the proportions hold.
What aspect ratio is my image?
Divide width by height and simplify. 1920 by 1080 gives 1.78, which is 16:9. The tool reduces the numbers by their greatest common divisor and tells you if the result matches a standard ratio.
What is the difference between 16:9 and 16:10?
16:10 is slightly taller. It was common on laptops for years because the extra vertical space suits documents and code, whereas 16:9 matches video and avoids letterboxing. Most laptops moved to 16:9, and some have moved back.
Why does my image get cropped on social media?
Because the platform displays a fixed ratio and your image is a different shape, so it trims the excess. Match the target ratio before uploading and you control what is kept rather than leaving it to an algorithm that often cuts through faces.
Can I calculate a ratio from just one dimension?
No. A ratio is a relationship between two numbers, so one dimension alone tells you nothing about shape. Give either both original dimensions, or a ratio plus one dimension.