Screen Resolution / Aspect Ratio Calculator
Enter a resolution to get its simplified aspect ratio and megapixel count, or compare two resolutions.
Last updated
How to work out an aspect ratio
- Enter a resolution’s width and height in pixels.
- Read its simplified aspect ratio, common name and megapixels.
- Optionally enter a second resolution to compare them.
About this tool
The aspect ratio is the width and height divided by their greatest common divisor — 1920×1080 shares a GCD of 120, reducing to the familiar 16:9. "Common name" matches against widely-used ratios (16:9, 4:3, 21:9, 16:10, 3:2, 1:1, 5:4) within a small tolerance, since real-world resolutions don't always reduce to a perfectly clean fraction.
Nothing you enter here is sent to a server — the entire tool runs as JavaScript in your browser tab.
Questions about screen resolutions
What aspect ratio is 1920 × 1080?
16:9, the standard for TVs, monitors and YouTube. It’s also called Full HD or 1080p, and is about 2.07 megapixels.
What resolution is 4K?
3840 × 2160 for TVs and monitors (UHD), also 16:9: four times as many pixels as 1080p.
What is 21:9?
Ultrawide, as on monitors such as 3440 × 1440 (strictly 43:18, but sold as 21:9).
How do I resize an image without stretching it?
Keep the same aspect ratio: divide the new width by the ratio’s width and multiply by its height. For 16:9 at 1280 wide, the height is 720.