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Aspect Ratio Calculator: Find Ratio or Resize to Fit

This free aspect ratio calculator reduces any width and height to a simple ratio such as 16:9, and works out the matching height or width when you resize an image or video.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

An aspect ratio keeps an image or video from being stretched. When you resize, one side must follow the other. This tool finds the simple ratio and the matching size.

Enter the width and height, and a new size if you want to scale.

How to Use This Tool

  1. Choose what to find.
  2. Enter the original width and height.
  3. Enter the new width or height if scaling.
  4. Press Calculate.

How the Calculation Works

The ratio is the width and height divided by their greatest common divisor. For a new height: new width × height ÷ width. For a new width: new height × width ÷ height. The tool also names the closest common ratio.

Worked Example

1920 by 1080 is 16:9. Scaling it to 1280 wide gives 720 high. A 1080 by 1350 post is 4:5.

Common Uses

  • Resizing images and video.
  • Social media sizes.
  • CSS aspect-ratio values.
  • Screen and print layouts.

Tips and Common Mistakes

  • Round to whole pixels at the end.
  • Use the CSS aspect-ratio property with the ratio shown.
  • Crop instead of stretching if the ratios differ.

Next, you may need the px to rem converter, CSS clamp calculator, border radius generator, box shadow generator.

Everything runs in your browser. Nothing you type is uploaded, stored or sent to any outside service.

Frequently Asked Questions

The proportion of width to height, written as two numbers such as 16:9. A 1920 by 1080 image has a ratio of 16:9.
Multiply the new width by the original height and divide by the original width to get the new height.
16:9 for video and screens, 4:3 for older screens, 1:1 for square posts, 3:2 for photos and 9:16 for vertical video.
Some sizes do not divide evenly. 1366 by 768 is very close to 16:9 but not exact.

Disclaimer: results are calculated in your browser from the numbers you enter. Check important results before you rely on them for money, health, safety or legal decisions.