About this tool
What is the aspect ratio of 1920 × 1080? How tall is a 16:9 video at 1280 pixels wide? This calculator reduces any size to its aspect ratio, shows it as a decimal (e.g. 1.78:1) too, and recognises common formats like 16:9, 4:3, 9:16 for stories or 21:9 for ultrawide monitors.
In the second part you scale a ratio to a new size: enter a width or a height, and the other side is calculated – handy for resizing images, videos, embeds or layout boxes. The unit does not matter: pixels, centimetres or inches all work the same. To crop images directly, use the Crop & Rotate Image; to convert CSS sizes, use PX to REM Converter.
How it works
- Enter width and height at the top, e.g. the resolution of a video or photo.
- Read the aspect ratio; if it matches a common format, its typical use is shown below.
- Take the ratio over with “Use this ratio below” or pick one of the common formats.
- Enter a new width or height – the other side is calculated automatically.
Frequently asked questions
How is the aspect ratio calculated?
Width and height are divided by their greatest common divisor. For 1920 × 1080 that is 120, so 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9 – the ratio is 16:9. For decimals the calculator finds the closest fraction with a denominator of at most three digits.
Why does my ultrawide monitor show 64:27 instead of 21:9?
“21:9” is a marketing name. 2560 × 1080 is exactly 64:27 (2.37:1), 3440 × 1440 exactly 43:18 (2.39:1). Both are close to 21:9 (2.33:1), so the tool recognises such sizes as ultrawide.
What does “Close to” mean?
If a size is less than 1 % away from a common format, the tool names that format. 1366 × 768, for example, is 683:384 mathematically but is sold as 16:9.
Which unit do I have to use?
Any – width and height just have to use the same unit. When scaling you get the result in the same unit, optionally rounded to whole numbers (useful for pixels).