What is an aspect ratio?
The aspect ratio of an image, a video or a screen is the relationship between its width and its height, written as two numbers with a colon. A picture that is 1920 pixels wide and 1080 pixels high has the ratio 1920:1080, which simplifies to 16:9. Two pictures with the same ratio have the same shape, even if one is much larger than the other.
Knowing the ratio helps you resize without stretching, crop to the format a platform wants, design layouts and choose the right export size for video.
How to use the aspect ratio calculator
- Enter the width and height of your image, video or screen in pixels.
- Read the simplified ratio, the decimal value and the orientation.
- To resize, enter a new width to get the matching height, or a new height to get the matching width.
- Compare with the table of common ratios to see which format yours is closest to.
How to resize without distortion
To keep the shape of a picture, the new width divided by the new height must equal the original width divided by the original height. If you know the new width, multiply it by the original height and divide by the original width to get the new height. For a 1920 x 1080 image resized to 1280 pixels wide, the height is 1280 x 1080 / 1920 = 720.
If the new size has a different ratio, you have to crop part of the picture or add bars. Changing only one side stretches or squashes the content.
Ratios for social media and video
- 16:9 is the standard for YouTube, most video and widescreen displays.
- 9:16 is the vertical format for Stories, Reels, Shorts and TikTok, typically 1080 x 1920.
- 4:5 is the tall portrait format for Instagram feed posts, typically 1080 x 1350.
- 1:1 is the square format for profile pictures and square posts, typically 1080 x 1080.
- 21:9 is used for ultrawide monitors and cinematic video.
- Platform recommendations change, so check the current guidelines before you export.
Aspect ratio and resolution
Aspect ratio describes shape, while resolution describes the number of pixels. A 1280 x 720 and a 3840 x 2160 video both have a 16:9 ratio, but the second has four times as many pixels. When you see a size such as 1366 x 768 that does not simplify to a neat ratio, the tool shows the closest standard ratio, which here is 16:9.
Example: preparing a video for different platforms
A 3840 x 2160 video is 16:9, which suits YouTube. To post it as a vertical clip you would crop to 9:16, which at the same height of 2160 pixels is 1215 pixels wide, and you would lose most of the sides of the frame. The calculator shows these sizes and reminds you that a different ratio always means cropping or adding bars. Plan the framing of your shot for the platform you care about most.
Common aspect ratios
| Ratio | Typical use | Example size |
|---|---|---|
| 16:9 | HD video, YouTube, most monitors | 1920 x 1080 |
| 4:3 | Older TVs, iPad, presentations | 1024 x 768 |
| 3:2 | 35 mm photos, DSLR cameras | 3000 x 2000 |
| 1:1 | Square posts, profile photos | 1080 x 1080 |
| 9:16 | Stories, Reels, Shorts, TikTok | 1080 x 1920 |
| 4:5 | Instagram portrait posts | 1080 x 1350 |
| 21:9 | Ultrawide monitors, cinema | 2560 x 1080 |
Frequently Asked Questions
How do I calculate the aspect ratio?
Divide the width and the height by their greatest common divisor. 1920 x 1080 gives 16:9.
How do I resize an image and keep the aspect ratio?
Enter the new width in the tool and use the height it calculates, or the other way around.
What is 1920x1080 in aspect ratio?
16:9.
What is the aspect ratio of a phone screen?
Many phones are about 19.5:9 or 20:9, although the exact ratio varies by model.
What is the difference between aspect ratio and resolution?
Aspect ratio is the shape, resolution is the number of pixels.
Can I resize my picture here?
The calculator gives you the sizes. To resize the actual image, use the Image Resizer tool.
Is my data uploaded?
No. The calculation runs in your browser.