The short answer
Why use Aspect Ratio?
Dividing pixel sizes by hand and finding the common factor is slow, and odd sizes rarely reduce cleanly. The tool does the math and tells you which standard ratio the picture is nearest to.
The ratio is width and height divided by their greatest common divisor, so 6000 × 4000 reads 3:2 and 1080 × 1350 reads 4:5. If the reduced ratio is not one of the common shapes, the line also shows the decimal against 1, and names the nearest common ratio when it is within 2%.
Portrait and landscape are different ratios here: 1080 × 1920 is 9:16, not 16:9. Phone photos follow their orientation tag, so a vertical shot reads as 3:4 even though the camera stored it as 4:3. Screenshots rarely match a standard shape: a 1179 × 2556 iPhone screenshot reduces to 131:284, or 0.461:1, taller than any print format.
To change the ratio, Crop Image has ratio presets, and Square Image pads a picture to 1:1 with a background color instead of cutting anything off. Size Finder and Megapixel give the same report with their own figures explained. All three save their report as a .txt file named after your image.
Where Aspect Ratio fits
Video thumbnails
Confirm a thumbnail is 16:9 before uploading it to a video platform.
Social posts
Check whether a photo fits a 4:5 portrait post without cropping.
Photo frames
See if a 3:2 camera photo will fit a 4:3 or 5:4 frame.
Start to finish
How to use Aspect Ratio
- 01Tap Choose image, or paste the screenshot or banner you want to check.
- 02Tap Apply changes and read the Aspect ratio line, with its decimal and nearest common ratio when not exact.
- 03Save the report with Download result, or go to Crop Image if the shape needs to change.
What to expect from Aspect Ratio
| Check | What it means here |
|---|---|
| Supported input | JPEG, PNG, WebP, GIF, BMP, SVG and browser-supported AVIF images |
| Main controls | Choose a file; the results are read-only |
| Output | Dimensions, metadata, colors, or an extracted preview, depending on the tool |
| Working limit | 50 MB and 50 megapixels per image |
Aspect Ratio tips
- Within 2% of a common ratio, the line adds close to, such as close to 16:9.
- 1080 × 1920 is 9:16; portrait and landscape count as different ratios.
- Instagram portrait posts use 4:5, which is 1080 × 1350.
- Square Image pads to 1:1 instead of cutting anything off.
Aspect Ratio FAQ
Something missing? Ask us.
Why does my image show a strange ratio like 683:384?
Which common ratios does it compare against?
How do I change the ratio?
Does Aspect Ratio upload my file?
Is Aspect Ratio free to use?
Why did Aspect Ratio fail or look wrong?
Related tools
More in Image Information.