Aspect Ratio Calculator

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Aspect Ratio Calculator

Work out the missing width or height for any aspect ratio, simplify the ratio of any two dimensions, and check the megapixel count.

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An aspect ratio calculator finds the missing dimension when you know one side and the ratio you need. Enter a width at 16:9 and it returns the matching height, and entering any two dimensions gives you their simplified ratio.

Runs entirely in your browser · no signup · nothing is uploaded · updated 2026-09-26

Ratio
16:9
Simplified
16:9
Megapixels
2.07

How to use it

  1. 1.Pick a common ratio, or type any width and height.
  2. 2.Change either dimension and the other follows the locked ratio.
  3. 3.Read the simplified ratio and megapixel count underneath.

Common aspect ratios and sizes

A ratio is a shape, not a size. Every resolution listed against a ratio has the same shape and different sharpness.

RatioDecimalCommon sizesUsed for
16:91.7781280x720, 1920x1080, 3840x2160Video, YouTube, most displays
1.91:11.9101200x630Open Graph and social preview cards
4:31.3331024x768, 1600x1200Older displays, some slides
1:11.0001080x1080Instagram posts, avatars
4:50.8001080x1350Instagram portrait posts
9:160.5631080x1920Reels, Stories, TikTok
3:21.5006000x4000Most DSLR and mirrorless cameras
21:92.3702560x1080, 3440x1440Ultrawide monitors

Embed this aspect ratio calculator on your site

Free to use on any blog, class page or wiki. Paste the snippet and keep the credit line under it.

Embed code
<iframe src="https://rankcert.com/embed/aspect-ratio-calculator" title="Aspect Ratio Calculator" width="100%" height="600" style="border:0;border-radius:12px" loading="lazy"></iframe>
<p style="font-size:13px">Free <a href="https://rankcert.com/tools/aspect-ratio-calculator">aspect ratio calculator</a> by RankCert</p>

Frequently asked questions

What is 16:9 in pixels?

Any pair where width divided by height is 1.778 - 1280x720, 1920x1080, 2560x1440 and 3840x2160 are all 16:9. The ratio does not specify a size.

How do I calculate an aspect ratio from two dimensions?

Divide both by their greatest common divisor. 1920 and 1080 share a divisor of 120, giving 16:9.

What aspect ratio should a YouTube thumbnail be?

16:9, at 1280x720. Instagram posts are 1:1 or 4:5, Stories and Reels are 9:16, and an Open Graph image is 1.91:1 at 1200x630.

What is the difference between aspect ratio and resolution?

Ratio is the shape; resolution is the number of pixels. 1280x720 and 3840x2160 have identical shapes and very different sharpness.

How do I keep an aspect ratio in CSS?

Use the aspect-ratio property: aspect-ratio: 16 / 9. It is supported everywhere now and replaces the old padding-top percentage hack.

What is 21:9 actually?

A marketing name for ultrawide monitors, which are usually 2560x1080 (64:27) or 3440x1440 (43:18). Neither is exactly 21:9.

Why does my video have black bars?

The video's ratio does not match the display's, so the player letterboxes it rather than cropping or stretching. Matching the ratio at export removes them.

How many megapixels is 4K?

About 8.3 for 3840x2160. 1080p is 2.1 and 8K is 33.2.

The guide behind this tool

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