Aspect Ratio Calculator
Find the aspect ratio of any resolution, or calculate missing dimensions for a given ratio.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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This calculator works in two modes. Choose the mode that fits your task:
- Find ratio from dimensions. Enter the pixel width and height of an image, video, or screen. The calculator reduces the ratio to its simplest form using the greatest common divisor. For example, 1920x1080 becomes 16:9.
- Resize to a given ratio. Enter your desired aspect ratio (e.g. 16 and 9) and one known dimension. Leave the other blank, and the calculator fills it in. Useful for cropping, exporting, or planning a layout without distortion.
Results update instantly. Use Copy to copy the ratio, or Share to send a pre-filled link.
About Aspect Ratios
An aspect ratio describes the proportional relationship between a rectangle's width and height. It is written as W:H — two integers reduced to their lowest common terms. The same ratio can describe any resolution: 640x360, 1280x720, and 3840x2160 all simplify to 16:9 because they share the same proportions.
Common aspect ratios include 16:9 (modern widescreen HD and 4K monitors, YouTube, most smartphones in landscape), 4:3 (old TV sets, many tablets in portrait), 21:9 (ultrawide cinema monitors), and 1:1 (square, used on Instagram). Photographers often work with 3:2 (matching 35mm film), while many mirrorless cameras default to 4:3.
Frequently Asked Questions
What aspect ratio is 1920x1080?
1920x1080 is a 16:9 aspect ratio. This is the standard for full HD (1080p) video, most modern monitors, and YouTube. Dividing both numbers by their GCD of 120 gives 16 and 9.
How do I resize an image without distortion?
To resize without distortion, keep the same aspect ratio. Enter your original ratio in Resize mode, type your new width, and the calculator computes the matching height. If you crop to a different ratio instead, some content will be cut from the edges.
What is the difference between 16:9 and 16:10?
16:9 is slightly wider relative to height than 16:10. At the same width, a 16:10 display is taller. 16:9 is the broadcast and streaming standard. 16:10 is common on MacBooks and older professional laptops because the extra vertical space helps with productivity tasks like documents and code.
What aspect ratio should I use for Instagram?
Instagram supports three ratios. Square posts are 1:1 (1080x1080 px). Portrait posts can be up to 4:5 (1080x1350 px), which takes up the most feed space. Landscape posts are 1.91:1 (1080x566 px). Reels and Stories use 9:16 (1080x1920 px) for full-screen vertical video.