Aspect Ratio Calculator
Calculate proportional width and height for any aspect ratio. Includes 16:9, 4:3, 1:1, 21:9 and custom ratio presets.
About Aspect Ratio Calculator
Work out the matching dimension when you resize an image or video and need the proportions to stay exact. Change any field and the others follow. Presets cover the standard video, photo and social formats.
How to use it
- Choose a preset ratio or enter a custom one.
- Type a known width or height.
- Read the matching dimension, rounded to whole pixels.
Frequently asked questions
What aspect ratio should I use for video?
16:9 for YouTube and most players, 9:16 for Shorts, Reels and TikTok, 1:1 for square feed posts and 4:5 for the tallest allowed Instagram feed image.
Why is my result not a whole number?
Not every width divides evenly into a ratio. The tool rounds to the nearest pixel; a one-pixel difference is not visible, but for video prefer dimensions divisible by two.
How do I find the ratio of an existing image?
Enter its width and height and the tool reduces them to the simplest whole-number ratio using the greatest common divisor.
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