Aspect Ratio Calculator

Features

• Find a new width or height that keeps the ratio
• One-click presets: 16:9, 4:3, 3:2, 1:1, 21:9 and more
• Shows the simplified ratio and its decimal value
• Works for images, video, screens and print
• Runs entirely in your browser

How to use it

1. Enter your original width and height, or pick a preset.
2. Type the new width you want.
3. The matching height that avoids distortion appears instantly.
4. Or enter a new height to get the matching width.

What an aspect ratio really is

An aspect ratio is simply the relationship between width and height, written as two numbers like 16:9. It does not fix a size, only a shape: 1280 by 720, 1920 by 1080 and 3840 by 2160 are all 16:9, which is why a video scales cleanly between them. Distortion happens when you change width and height by different amounts, stretching circles into ovals and faces into funhouse mirrors. Keeping the ratio constant is what keeps everything looking right.

To resize without distortion you scale both dimensions by the same factor. If a 1920 by 1080 image needs to be 1280 wide, the factor is 1280 divided by 1920, and multiplying the height by that same factor gives 720. That is the whole calculation, and doing it the other way, fixing a height and solving for width, works identically. The tool simply does the arithmetic and rounds to whole pixels.

The simplified ratio comes from dividing both numbers by their greatest common divisor. 1920 and 1080 share a divisor of 120, which reduces them to 16 and 9, hence 16:9. Common shapes have names worth knowing: 16:9 is standard widescreen video, 4:3 is older screens and many photos, 1:1 is square social posts, 3:2 is classic 35mm photography, and 21:9 is ultrawide cinema.