Find an aspect ratio like 16:9 and work out a new width or height that keeps it.
How to Use Aspect Ratio Calculator
Enter the original width and height, or tap a preset such as 16:9 (1920 × 1080).
Read the simplified aspect ratio.
Type a new width or a new height. The other value is filled in to keep the same shape, and the scale percentage is shown.
What an aspect ratio is
An aspect ratio is width compared with height, written in its simplest form. 1920 × 1080 divides down to 16:9, the shape of most TVs, laptops and YouTube videos. 4:3 is older monitors and many tablets, 1:1 is square, and 9:16 is a vertical phone video. The calculator reduces your numbers by their greatest common divisor, so it shows the exact ratio.
Some sizes don't reduce to a familiar ratio. A 1366 × 768 laptop screen gives 683:384, which is very close to 16:9 but not exactly.
Scaling without distortion
To resize while keeping the shape, new height = new width × original height ÷ original width. Results can include decimals; round to whole pixels when you use them. Video encoders often prefer even numbers, so a height of 607.5 would become 608.
Key Features & Practical Use Cases
Working out the height of a 1280-pixel-wide version of a 1920 × 1080 video.
Checking whether an image is 16:9, 4:3 or square before uploading it.
Sizing a thumbnail, banner or embed without distorting it.
Planning print or screen layouts that keep a fixed ratio.
Frequently Asked Questions
What is the aspect ratio of 1920 × 1080?
16:9.
How do I calculate height from width and ratio?
Multiply the width by the ratio's height and divide by its width. For 16:9 at 1280 wide: 1280 × 9 ÷ 16 = 720.
Why isn't my ratio a familiar one like 16:9?
The calculator shows the exact ratio. Sizes that are almost 16:9, like 1366 × 768, reduce to unusual numbers.
Does it resize my image?
No, it only calculates sizes. Use the Image Resizer to change an image's dimensions.
About OneClickly
OneClickly is a set of 119 free tools for PDFs, images, text, everyday math and code. They run in your browser, so the files and text you work with stay on your device.
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