Aspect Ratio Calculator
Find an exact ratio from dimensions, or calculate a missing width or height while preserving proportions.
Choose a calculation
Enter positive whole-pixel dimensions to reduce them to an exact ratio.
Choose a ratio, then provide the side you know. The other pixel dimension is rounded to the nearest whole pixel.
Result appears here.
Orientation: Landscape
Common aspect ratios
| Ratio | Typical use | Example |
|---|---|---|
| 16:9 | HD/video example | 1920×1080 |
| 9:16 | Vertical video example | 1080×1920 |
| 4:3 | Classic display or presentation | 1024×768 |
| 3:2 | Photography | 3000×2000 |
| 1:1 | Square | 1000×1000 |
| 4:5 | Portrait social example | 1080×1350 |
| 16:10 | Display or laptop | 1920×1200 |
| 21:9 | Common ultrawide category label; exact pixel ratios can differ | Not every ultrawide is mathematically 21:9 |
How aspect ratios work
An aspect ratio is the relationship between width and height. Resolution is the actual pixel count: 1920×1080 and 1280×720 are different resolutions with the same 16:9 ratio.
Changing width and height independently can stretch or squeeze an image or video. This calculator uses the GCD(width, height) to simplify dimensions, such as 1920÷120 : 1080÷120 = 16:9.
FAQ
What is an aspect ratio?
It describes the proportional relationship between width and height.
How do I calculate height for 16:9?
Choose Resize by ratio, select 16:9, choose I know width, and enter the width.
Why is 3440×1440 not exactly 21:9?
Its exact reduced ratio is 43:18. 21:9 is a common category label, not the mathematical result for every ultrawide display.
Does this resize an image?
No. It calculates dimensions only; use an image tool afterward to resize or compress a file.
Are my values uploaded?
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Reviewed: 2026-09-21