Aspect Ratio Calculator
Find the aspect ratio of any size and resize an image or video without distortion — pick a preset or enter your own dimensions.
How the aspect ratio calculator works
The aspect ratio is simply the relationship between a picture's width and its height, written as two numbers like 16:9. This calculator reduces any width and height to their simplest ratio using the greatest common divisor, then lets you resize one dimension while it works out the other so the proportions never change. That is the trick to scaling an image, video frame or screen without the stretched, squashed look you get when the ratio drifts.
Type a width and height to see the ratio, or pick a common ratio chip to snap to it. To resize, enter a new width and the matching height appears instantly (and vice versa). Everything is rounded to whole pixels, which is what image editors and video tools expect.
Common aspect ratios and where they are used
| Ratio | Where you see it | Example size |
|---|---|---|
| 16:9 | Modern TVs, YouTube, most monitors and phone video | 1920 × 1080 |
| 9:16 | Vertical video — Reels, TikTok, Stories | 1080 × 1920 |
| 4:3 | Older monitors, many tablets, classic photos | 1024 × 768 |
| 3:2 | Most DSLR/mirrorless photos, some laptops | 3000 × 2000 |
| 21:9 | Ultrawide monitors and cinematic video | 2560 × 1080 |
| 1:1 | Square posts and profile images | 1080 × 1080 |
Ratio is not the same as resolution. 1280×720 and 1920×1080 are different resolutions but share the same 16:9 ratio. To work out pixel density and screen sharpness instead, use our screen resolution & DPI calculator.
Frequently asked questions
What does an aspect ratio like 16:9 mean?
It means that for every 16 units of width there are 9 units of height. The actual pixel count can vary — 1280×720, 1920×1080 and 3840×2160 are all 16:9 — but the shape of the frame stays the same.
How do I resize an image without stretching it?
Keep the same aspect ratio. Decide one new dimension (say a width of 800 pixels) and let the calculator set the matching height so the proportions are preserved. If you force both numbers to values that do not share the original ratio, the image will look stretched or squashed.
How do I convert 16:9 to a pixel size?
Pick the width you want and multiply by 9/16 for the height. For a 16:9 frame 1280 pixels wide, the height is 1280 × 9 ÷ 16 = 720 pixels. The calculator does this for you when you enter a new width.
What aspect ratio should I use for social media video?
Use 9:16 (vertical, e.g. 1080×1920) for TikTok, Reels and Stories, 1:1 (square) for feed posts, and 16:9 (e.g. 1920×1080) for standard YouTube and landscape video. Each platform crops to these shapes, so matching them avoids letterboxing.
Does cropping change the aspect ratio?
It can. Cropping removes pixels from the edges, so unless you crop symmetrically to a target ratio you will end up with a new ratio. Many editors let you lock a crop to a ratio such as 1:1 or 4:5 so the result is predictable.
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