Aspect Ratio Calculator
Enter dimensions to calculate ratio and check platform compatibility.
Common Standards
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What this tool does
The Aspect Ratio Calculator works out the aspect ratio (the shape) of any image or screen from its width and height. It also tells you which platform or standard that shape matches.
How to use it
Enter the width and height in pixels, or click a common size. The ratio, its decimal value and a scaled preview update as you type.
How it's calculated
The tool divides both numbers by their greatest common divisor. For 1920 × 1080, that's 120, giving 16:9. When the simplified numbers are large, as with 1366 × 768 (683:384), it shows the decimal form instead (1.78:1) and the nearest standard, marked with ≈ (here ≈ 16:9).
Common ratios
| Ratio | Used for |
|---|---|
| 16:9 | YouTube, HD and 4K TV, most monitors |
| 9:16 | TikTok, Reels, Shorts, Stories |
| 1:1 | Square posts |
| 4:5 | Instagram portrait posts |
| 3:4 | Instagram tall portrait, and the profile grid since 2025 |
| 1.91:1 | Instagram landscape, Facebook and LinkedIn link previews |
| 3:2 | Most camera photos |
| 2:3 | Pinterest pins |
| 4:3 | Older TVs, many tablets |
| 2.39:1 | Widescreen cinema |
Why photos look stretched or cropped
If an image's ratio doesn't match its frame, the app either stretches it, crops the edges or adds bars. Resize or crop to the target ratio first to choose what's kept. Our Social Media Photo Resizer does this for you.
Scaling an image to a new size
To keep the shape, scale the height by the same ratio as the width:
new height = new width × original height ÷ original width
A 1920 × 1080 image resized to 1200 pixels wide becomes 1200 × 1080 ÷ 1920 = 675 pixels high. The other way round, a 9:16 video that must be 1920 pixels tall is 1920 × 9 ÷ 16 = 1080 pixels wide. If the result isn't a whole number, round it; one pixel won't show.
Frequently asked questions
Is 21:9 really 21:9?
Not quite. Ultrawide monitors sold as 21:9 are usually 2560 × 1080 or 3440 × 1440, which are about 2.37:1 and 2.39:1. The calculator recognizes both.
Does ratio affect quality?
No; resolution (the number of pixels) does. Two images with the same ratio can be very different sizes.
How do I crop to a ratio without losing the subject?
Work out the crop size first. For a 4:5 crop of a 4000 × 3000 photo, keep the full height of 3000 pixels and make the crop 3000 × 4 ÷ 5 = 2400 pixels wide, then slide the crop box to frame the subject.
Sources: Meta for Developers, Images in Link Shares; Buffer, Social media image sizes (Instagram formats). Last reviewed on SuiteWebTools: October 2026.