What this calculator does
Aspect ratio is the shape of a screen, photo or video: width compared with height. A 1920 × 1080 screen is 16 : 9. This tool simplifies any size to its aspect ratio and, if you give it a new width or height, tells you the other side so nothing looks stretched.
How to use it
- Enter the original width and height in pixels (or inches, or anything, as long as both use the same unit).
- To resize, type either a new width or a new height.
- Press the button and read the ratio and the new size.
The method
Divide width and height by their greatest common divisor to get the ratio. To resize, keep the ratio equal: new height = new width × (old height ÷ old width).
Common aspect ratios
| Ratio | Typical use | Example size |
|---|---|---|
| 16 : 9 | Widescreen video, most monitors, YouTube | 1920 × 1080 |
| 4 : 3 | Classic TVs and older monitors | 1024 × 768 |
| 1 : 1 | Square social posts | 1080 × 1080 |
| 9 : 16 | Vertical video such as Stories and Reels | 1080 × 1920 |
| 3 : 2 | 35 mm film and many cameras | 3000 × 2000 |
| 21 : 9 | Ultrawide monitors and cinema | 2560 × 1080 |
Tips
- Round to whole pixels at the end, not in the middle of the calculation.
- If the new size does not match the ratio, you will need to crop or add bars to avoid stretching.
- Read the aspect ratio guide for how ratios are used in video and photography.
Read our short guide with worked examples you can follow on paper.
Frequently asked questions
How do I calculate an aspect ratio?
Divide width and height by their greatest common divisor. 1920 and 1080 share a divisor of 120, which gives 16 : 9.
How do I resize an image without stretching it?
Keep the aspect ratio. Multiply the new width by height ÷ width to get the new height.
What aspect ratio is 1920x1080?
16 : 9.
What is the aspect ratio for vertical video?
Usually 9 : 16, such as 1080 × 1920.
Does the unit matter?
Only that width and height use the same unit.