Aspect Ratio Calculator
Calculate canvas dimensions while preserving a specific aspect ratio
About Aspect Ratio Calculator
Keeps width and height in proportion for any aspect ratio: type one dimension and the other is recalculated, rounded to whole pixels. Twelve presets cover common formats such as 16:9, 4:3, 1:1, 9:16, 21:9, cinema ratios and DCI 4K, and a scaled preview shows the detected ratio with its decimal value. Useful for video frames, social media images, canvas sizes and responsive embeds.
Category: Media.
Frequently asked questions
What is aspect ratio?
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The proportional relationship between width and height. 16:9 means for every 16 units wide, the frame is 9 units tall. It stays constant regardless of the actual pixel dimensions.
Why does 1366×768 show as 683:384 instead of 16:9?
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The detected ratio is reduced exactly using the greatest common divisor, so sizes that are only close to a standard don't simplify to it: 1366×768 gives 683:384, and a 2560×1080 ultrawide gives 64:27 rather than 21:9. Compare the decimal value (1.779:1 versus 1.778:1 for true 16:9) to see how close it is.
What aspect ratio should I use for social media?
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Instagram feed: 1:1 (square) or 4:5 (portrait). Stories, Reels, TikTok and YouTube Shorts: 9:16. Regular YouTube videos: 16:9. Link preview images on Facebook and LinkedIn: about 1.91:1, usually 1200×630.
What is the difference between 2.39:1 and 2.35:1?
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Both are anamorphic widescreen ratios. 2.35:1 was the standard until a 1970 SMPTE revision of the projector aperture turned it into 2.39:1, which is today's DCI scope container (2048×858) and is often rounded to 2.40:1. On screen the difference is barely noticeable.