Stretch a photo or video to the wrong shape and faces look squashed, circles turn into ovals and logos warp. Keeping the aspect ratio, the proportion between width and height, avoids that, and it matters everywhere: video exports, YouTube thumbnails, Instagram posts, presentation slides, website images, TV and monitor sizes, and print. This free aspect ratio calculator handles the everyday jobs. Enter any width and height to find the ratio. It's reduced to its simplest form, so 1920 × 1080 becomes 16:9, and for odd sizes it also gives the nearest common ratio and the decimal value (1.78:1). Or choose a ratio such as 16:9, 4:3, 3:2, 1:1, 4:5, 9:16 or 21:9, or type your own, then enter a new width to get the matching height, or a height to get the width. That's how you resize without distortion. A live preview rectangle shows the shape, and a list of standard sizes for the chosen ratio (720p, 1080p, 4K and others) is one click away. There's a quick reference for platforms too: YouTube is 16:9, Instagram feed posts 4:5 or 1:1, Stories, Reels, Shorts and TikTok 9:16, and Facebook and LinkedIn link images 1.91:1. Values can be rounded to whole or even pixels, because many video codecs require even dimensions. Everything runs in your browser.
Find a ratio
Resize keeping the ratio
Common aspect ratios
| 16:9 | YouTube, TVs, monitors, slides |
| 9:16 | Stories, Reels, Shorts, TikTok |
| 4:5 | Instagram portrait posts |
| 1:1 | Square posts, profile images |
| 3:2 | Most camera photos |
FAQ
How do I calculate an aspect ratio?
Divide width and height by their greatest common divisor: 1920×1080 ÷ 120 = 16:9.
Why does my video need even numbers?
Many video codecs (like H.264) require even width and height. Use “Even pixels”.
Is 1366×768 really 16:9?
Almost: it’s 683:384, which is 1.779:1, very close to 16:9 (1.778).
Is anything uploaded?
No. All calculations are local.
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