How to use the Aspect Ratio Calculator
- Enter the original width and height, or pick a common ratio such as 16:9.
- Read the simplified ratio, its decimal value and the closest standard ratio.
- Type a new width or height under Resize: the other side is calculated for you.
- Copy the result, or the CSS
aspect-ratiorule.
Common aspect ratios
| Ratio | Used for | Example sizes |
|---|---|---|
| 16:9 | HD video, YouTube, TVs, most monitors | 1280 × 720, 1920 × 1080, 3840 × 2160 |
| 9:16 | Phone video: TikTok, Reels, Shorts, Stories | 1080 × 1920 |
| 4:3 | Older TVs, iPad, many compact cameras | 1024 × 768, 1600 × 1200 |
| 3:2 | DSLR photos, 6 × 4 inch prints | 6000 × 4000 |
| 1:1 | Square posts, profile pictures | 1080 × 1080 |
| 4:5 | Instagram portrait posts | 1080 × 1350 |
| 21:9 | Ultrawide monitors, cinema | 2560 × 1080, 3440 × 1440 |
| 16:10 | Laptops and MacBooks | 1440 × 900, 2560 × 1600 |
How to calculate an aspect ratio
Divide the width and height by their greatest common divisor. For 1920 × 1080, the largest number that divides both is 120, giving 16 × 9. To resize, keep the ratio: new height = new width × original height ÷ original width. So a 1280-pixel-wide 16:9 video is 1280 × 9 ÷ 16 = 720 pixels tall.
Some sizes don't simplify neatly. 1366 × 768 is exactly 683:384, but it's sold as 16:9 because it's very close; the calculator shows the nearest standard ratio too.
To make a photo fit a ratio, use Crop Image (choose 16:9, 4:5 and so on) or the Image Resizer on our sister site, curlytab.
Frequently asked questions
What is the aspect ratio of 1920 × 1080?
16:9.
What size is 16:9 at 1080 pixels wide?
1080 × 608 (607.5, rounded). For 9:16 portrait video at 1080 wide, the height is 1920.
How do I keep an aspect ratio in CSS?
Use aspect-ratio: 16 / 9; with a width, and the browser sets the height for you.
Is 4:3 the same as 1.33:1?
Yes. 4 ÷ 3 = 1.33. Ratios are often written as a decimal against 1, like 2.39:1 for widescreen cinema.
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