Aspect ratio calculator
Compute width, height and ratio, with standard resolutions.
- Instant
- Free
- Private (processed locally)
- No sign-up
Resizing without distortion
Shrinking an image while keeping its proportions avoids the “squashed” look. This tool infers the missing dimension as soon as you lock the ratio, and shows the matching standard resolutions.
-
Enter two dimensions
Width and height; the ratio is computed via GCD.
-
Lock the ratio
Change one dimension and the other follows automatically.
-
Pick a resolution
The list filters the standard sizes for that ratio.
Common ratios and resolutions
| Resolution | Ratio |
|---|---|
| 1920 × 1080 | 16:9 |
| 1280 × 720 | 16:9 |
| 800 × 600 | 4:3 |
| 1024 × 1024 | 1:1 |
| 1920 × 1200 | 16:10 |
Everything is computed in your browser. The ratio is always reduced to its simplest form via the GCD.
Frequently asked questions
How is the ratio calculated?
Width and height are divided by their greatest common divisor (GCD). For example, 1920 × 1080 has a GCD of 120: 1920/120 = 16 and 1080/120 = 9, giving the ratio 16:9. 800 × 600 gives 4:3.
What is the ratio lock for?
When enabled, changing the width automatically adjusts the height (and vice versa) to keep the same ratio. It is perfect for resizing an image or video without distorting it.
Why is 16:9 so common?
It is the ratio of modern HD screens and video: 1280 × 720, 1920 × 1080 (Full HD) and 3840 × 2160 (4K) are all 16:9. YouTube, TVs and most monitors use it by default.
What is the difference between ratio and resolution?
The ratio is a proportion (16:9), with no unit; the resolution is a size in pixels (1920 × 1080). Several resolutions share the same ratio: 1280 × 720 and 1920 × 1080 are both 16:9.