This free aspect ratio calculator solves the one problem every designer, video editor and content creator hits weekly: given a width, a height or a ratio, what is the missing number? Enter any two values and the tool finds the third instantly — plus matching sizes for your ratio. No sign-up, nothing uploaded.
Common ratios:
How to Use the Aspect Ratio Calculator
- To find a ratio: enter a width and a height (for example 1920 and 1080) and click Calculate — the aspect ratio calculator gives the simplified ratio.
- To find a missing side: pick a preset ratio (16:9, 9:16, 1:1, 4:3, 3:2 or 21:9) or type your own, enter either the width or the height, and click Calculate.
- The tool also lists common sizes at your ratio, so you can pick the nearest standard size for export.
What Is Aspect Ratio?
An aspect ratio is the proportional relationship between an image or video’s width and its height, written as width:height. A 16:9 video is 16 units wide for every 9 units tall, whatever the actual pixel size. That is why a 1920×1080 video and a 1280×720 video look identical in shape — both are 16:9. The concept of aspect ratio applies to screens, photos, print and social posts alike.
Getting the ratio wrong is how images get stretched or cropped badly. Social platforms each prefer a ratio: 16:9 for YouTube videos, 9:16 for vertical reels and stories, 1:1 for square feed posts, and 4:3 for classic photos. Design at the right ratio from the start and nothing gets cut off. The concept of aspect ratio is worth a quick read before you resize anything important.
Common Aspect Ratios
| Ratio | Used for | Example size |
|---|---|---|
| 16:9 | YouTube, TV, presentations | 1920 × 1080 |
| 9:16 | Reels, Shorts, stories | 1080 × 1920 |
| 1:1 | Square posts, profile pictures | 1080 × 1080 |
| 4:3 | Classic photos, old TV | 1600 × 1200 |
| 3:2 | DSLR photos, print | 3000 × 2000 |
| 21:9 | Ultrawide monitors, cinema | 3440 × 1440 |
Frequently asked questions
How does the aspect ratio calculator simplify a ratio?
It divides both numbers by their greatest common divisor. 1920 and 1080 share the divisor 120, so 1920÷120 : 1080÷120 = 16:9.
Can I use it for print sizes?
Yes. Enter inches or centimetres instead of pixels — the ratio maths is identical. Only the unit label changes.
What is the difference from the screen resolution checker?
The screen resolution checker detects your own device’s display. This aspect ratio calculator works out proportions for any size you type in.
Are my dimensions stored?
No. The calculation runs in your browser only.
Related tools: Screen Resolution Checker, Image Compressor, Image Resizer.
