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Aspect Ratio Calculator: Simplify a Ratio and Resize

Enter a width and height to get the simplified ratio and its closest common format, then plug in a new width to see the matching height, free.

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Simplified ratio
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Decimal ratio
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Closest common format
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Matching new height
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An aspect ratio is just a width to height comparison reduced to its simplest form, like 16:9 for widescreen video or 1:1 for a square post. This calculator takes any pixel dimensions, reduces them to the smallest matching whole numbers, tells you the closest standard format, and if you give it a new width it works out the exact height you need to resize to without stretching or squashing the image.

How this calculator simplifies a ratio

The simplified ratio is found using the greatest common divisor, the largest number that divides evenly into both the width and the height. Dividing both numbers by that value gives the smallest whole-number ratio that describes the same proportions. For example, 1920 and 1080 share a greatest common divisor of 120, so dividing both by 120 gives 16 and 9, the familiar 16:9 widescreen ratio.

Common aspect ratios and where they are used

16:9 is the standard for YouTube, widescreen video and most desktop monitors. 9:16 is the vertical equivalent used for Instagram Reels, TikTok and YouTube Shorts. 1:1 square still works well for Instagram feed posts and product photos. 4:5 is the tallest ratio Instagram's feed will display without cropping, which makes it popular for maximizing space in a scrolling feed. 21:9 is the ultra-wide cinematic ratio used in film and some monitor hardware.

How to resize an image or video without distorting it

To resize without stretching, the new height has to scale by the exact same factor as the new width. This calculator does that by multiplying your new width by the original height divided by the original width. If your source is 1920 by 1080 and you resize to a width of 800px, the matching height is 800 multiplied by 1080 divided by 1920, which comes out to 450px, keeping the 16:9 proportions intact.

Getting your visuals right is one small part of a page that actually converts and ranks. If you want a broader look at what is holding your content back, request a free SEO audit and we will show you where to focus first.

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FAQ

Aspect Ratio Calculator: questions, answered

How do I simplify an aspect ratio?
Divide both the width and the height by their greatest common divisor, the largest number that fits evenly into both. This calculator does that automatically: enter your pixel dimensions and it returns the smallest whole-number ratio that describes the same shape, such as 1920x1080 simplifying to 16:9.
What aspect ratio should I use for Instagram, TikTok or YouTube?
TikTok, Instagram Reels and YouTube Shorts all use 9:16 vertical video. Instagram feed posts work best at 4:5 or 1:1. Standard YouTube video and most widescreen content uses 16:9. Always check the platform's current specs before a big upload, since recommended sizes do change.
How do I resize an image and keep the same aspect ratio?
Enter your original width and height, then enter the new width you want in the resize field. The calculator multiplies that new width by your original height-to-width ratio to give you the exact height that preserves the same proportions, so the image will not look stretched or squashed.
What is the difference between 16:9 and 9:16?
They are the same ratio rotated 90 degrees. 16:9 is wider than it is tall and is the standard for landscape video and monitors. 9:16 is taller than it is wide and is the standard for vertical video formats like Stories, Reels and Shorts.
Why does my ratio not match a common preset exactly?
Real-world images and screenshots are rarely cropped to a perfectly round ratio. The calculator shows the closest standard format and how far off it is as a percentage, so you can decide whether to crop slightly to hit an exact 16:9 or 1:1, or leave it as a custom ratio.

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