Aspect Ratio
The proportional relationship between an image's width and height, expressed as width:height (e.g. 16:9 or 4:3).
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What Is Aspect Ratio?
Aspect ratio is the proportional relationship between an image's width and height, written as width:height. A 1920×1080 image has an aspect ratio of 16:9 (both numbers divide by 120). A 800×600 image is 4:3.
Common Aspect Ratios
| Ratio | Common Use |
|---|---|
| 16:9 | Widescreen video, desktop monitors, YouTube thumbnails |
| 4:3 | Older monitors, standard definition video |
| 1:1 | Instagram square posts, profile photos |
| 4:5 | Instagram portrait posts |
| 9:16 | Stories (Instagram, TikTok, Snapchat) |
| 3:2 | DSLR camera sensor, standard photo prints |
| 2:1 | Twitter/X header images |
| A4 paper | 1:√2 ≈ 1:1.414 |
Why Aspect Ratio Matters When Resizing
If you resize an image without maintaining its aspect ratio, you distort it — people look stretched or squashed, circles become ovals.
The safe way to resize: lock the aspect ratio and change only one dimension. The other dimension adjusts automatically to maintain the proportional relationship.
Example: A 1200×800 image (3:2) resized to 800 wide → height becomes 800 × (800/1200) = 533 px (not 600 px).
Platform Crop Behaviour
Social media platforms crop uploaded images to their required aspect ratio. If your image has a different ratio, the platform centres the crop — cutting off top/bottom or left/right edges.
Solution: Resize to exact platform dimensions before uploading rather than letting the platform crop automatically. Use our Resize Image tool to set the exact pixel dimensions required.