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The Ultimate Guide to Image Aspect Ratio
Whether you are a web developer, video editor, or social media manager, understanding aspect ratio is the difference between a professional look and a distorted, stretched mess. This guide explains everything you need to know about calculating and resizing dimensions correctly.
What is Aspect Ratio?
Aspect ratio is the proportional relationship between the width and height of an image or screen. It is not a measurement of physical size (like inches or centimeters), but rather a ratio of dimensions.
For example, a ratio of 16:9 means that for every 16 units of width, there are 9 units of height. It doesn't matter if those units are pixels, inches, or meters—the shape remains the rectangle we associate with modern televisions.
The Formula
To calculate the aspect ratio of an image manually, you divide the width by the height. To find new dimensions while maintaining that ratio, use this formula:
*Our calculator above does this math for you instantly.*
Common Aspect Ratios Explained
| Ratio | Name | Best Used For |
|---|---|---|
| 16:9 | Widescreen | Standard for YouTube, HDTV, and most laptop screens. (e.g., 1920x1080). |
| 9:16 | Vertical | The standard for mobile video: TikTok, Instagram Reels, and YouTube Shorts. |
| 4:3 | Standard | Old CRT TVs, iPads, and Micro Four Thirds photography cameras. |
| 1:1 | Square | Instagram posts and profile pictures (Avatars). |
| 21:9 | Ultrawide | Cinematic movies (CinemaScope) and ultrawide gaming monitors. |
Why Images Get Distorted
Distortion (stretching or squashing) happens when you force an image into a container that has a different aspect ratio than the image itself.
- Letterboxing: Adding black bars to the top and bottom (e.g., watching a movie on a square TV).
- Cropping: Cutting off the edges to fill the screen (often done by Instagram).
- Stretching: Forcing the image to fit, which makes circles look like ovals and people look thin or wide.
Using the Omni Flow Kit Dimension Calculator allows you to find the exact pixel dimensions required to fit your content perfectly without stretching.
Social Media Cheat Sheet (2025)
Save time by using these standard pixel dimensions for your projects:
- Profile: 320 x 320 (1:1)
- Square Post: 1080 x 1080 (1:1)
- Portrait: 1080 x 1350 (4:5)
- Story/Reel: 1080 x 1920 (9:16)
- Thumbnail: 1280 x 720 (16:9)
- Channel Art: 2560 x 1440
- Video: 1920 x 1080 (HD)
- Shorts: 1080 x 1920 (9:16)
- Cover Photo: 1128 x 191
- Shared Image: 1200 x 627
- Profile Pic: 400 x 400