Find the aspect ratio of any width and height, and scale dimensions proportionally.
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How do you calculate an aspect ratio?
The ratio is width:height divided by their greatest common divisor; a new height = new width × (height ÷ width). For example, 1920 × 1080 reduces to 16:9 (1.778:1), and scaled to 1280 wide the height is 720. Common ratios include 16:9 (widescreen), 4:3 (classic), 1:1 (square) and 21:9 (ultrawide).
Understanding your result
Common ratios include 16:9 (widescreen), 4:3 (classic), 1:1 (square) and 21:9 (ultrawide).
Formula and method
The ratio is width:height divided by their greatest common divisor. A new height = new width × (height ÷ width).
Assumptions and limitations
The calculator reduces the numbers you enter and scales one dimension from the other; it does not crop, resize or open image files, and it cannot judge whether a ratio suits a particular platform. It also will not add letterboxing or tell you how content will be cropped by a given container.
Worked example
1920 × 1080 reduces to 16:9 (1.778:1). Scaled to 1280 wide, the height is 720.
How to use this tool
- Enter the width and height.
- Optionally enter a new width to get the matching height.
- Press Calculate.
About the Aspect Ratio Calculator
The Aspect Ratio Calculator reduces any width and height to its simplest ratio and helps you resize images or video while keeping the proportions correct.
Who should use this tool
Video editors, designers, photographers and web developers who need dimensions to stay proportional when resizing. Also useful for anyone preparing images for social media, presentations or print who wants to avoid stretched or squashed results.
Benefits
- Reduces any width and height to its simplest ratio
- Scales a new dimension while keeping proportions exact
- Identifies common ratios such as 16:9, 4:3 and 1:1
- Completely free, with no registration or paywall
Practical use cases
- Resizing an image without stretching or distortion
- Checking whether footage fits a 16:9 frame
- Working out a matching height for a new width
- Preparing artwork to a required social or print ratio
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Frequently asked questions
How do I keep an image in proportion?
Enter the original width and height, then a new width — the calculator gives the height that preserves the ratio.
What does a ratio like 16:9 actually mean?
It describes the relationship between width and height, not a fixed size. A 16:9 image is 16 units wide for every 9 units tall, so 1920 by 1080 and 1280 by 720 share the same shape. Any size keeping that proportion looks identical, just larger or smaller.
Why is my ratio not a familiar one?
Because your dimensions simply do not reduce to a standard shape. Photos from cameras and phones often land on ratios like 3:2 or 5:4 rather than 16:9. That is normal; the calculator shows the true simplest ratio of whatever width and height you enter.