Aspect Ratio Calculator
Free. Runs in your browser; files are not uploaded.
Original size or ratio
Type pixels such as 1920 and 1080, or a ratio such as 2.39 and 1. Pasting 1920x1080 into either field fills both.
Aspect ratio
16:9
Landscape · 1.78:1
Resize with the same ratio
Change the width or the height. The other side follows the ratio.
Common 16:9 sizes
Select a size to use it as the new size.
Runs locally in your browser. Files are processed on this device and are not uploaded.
How to calculate an aspect ratio
Enter the original size
Type the width and height in pixels, or a ratio such as 2.39:1. Pasting 1920x1080 into either field fills both.
Read the ratio
The simplified ratio, the orientation and the decimal ratio appear at once. 1920 × 1080 reads as 16:9, 1.78:1.
Set the new size
Type a new width to get the matching height, or a new height to get the matching width.
Copy the result
Copy the new size, or pick one of the common sizes for the current ratio.
What is an aspect ratio?
An aspect ratio is the width of an image divided by its height, written as two whole numbers. The calculator divides both sides by their greatest common divisor, so 1920 × 1080 becomes 16:9.
Two images with the same ratio have the same shape, whatever their pixel size. Resizing with the ratio locked avoids stretching.
| Ratio | Common sizes | Typical use |
|---|---|---|
| 16:9 | 1280 × 720, 1920 × 1080, 3840 × 2160 | Video, slides, most monitors |
| 16:10 | 1440 × 900, 2560 × 1600 | MacBook displays |
| 4:3 | 1024 × 768, 2048 × 1536 | iPad, older displays |
| 1:1 | 1080 × 1080 | Social posts, avatars |
| 9:16 | 1080 × 1920 | Stories, Shorts, phone screens |
Frequently asked questions
What aspect ratio is 1920 × 1080?
16:9. Both sides divide by 120, giving 16 and 9.
Can I enter a decimal ratio?
Yes. Type values such as 2.39 and 1. The calculator reduces them to whole numbers where possible.
How do I get the size of an image?
Select Use an image, or drop or paste one on the page. Only the pixel size is read, and the image stays in your browser.
Which ratios are listed as shortcuts?
16:9, 9:16, 4:3, 3:2, 1:1, 4:5, 21:9 and 16:10.
Why is the new size rounded?
Pixels are whole numbers, so the calculated side is rounded to the nearest pixel.
Related free tools
- Screenshot Resolution CheckerSee pixel size, file size, aspect ratio and print size of an image.
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- Split ImageCut one image into a grid of rows and columns and download the pieces.
- Image ConverterChange images between PNG, JPG and WebP, one file or a batch.
- Image CompressorReduce PNG, JPG and WebP file size and compare the result before saving.
- Compare ImagesCheck two versions with a slider, fade, side by side or a pixel difference view.
Need screenshots in a fixed aspect ratio?
Temposhot captures a fixed custom area on your Mac, so every screenshot in a run has the same size and ratio.
Free download. Apple Silicon, macOS 14 or later.