๐ Aspect Ratio Calculator
Height at the same ratio: 720
Enter a width and height to automatically calculate the simplest aspect ratio (e.g. 16:9). Enter a new width and this tool also calculates the matching height that preserves the same ratio. Useful for resizing video or images, or planning print dimensions.
How to use
- Enter the original width and height.
- The simplified aspect ratio and decimal ratio are shown automatically.
- Enter a "new width" to automatically calculate the height at the same ratio.
How the calculation works
This tool finds the greatest common divisor (GCD) of the width and height and divides both by it, reducing the aspect ratio to its simplest whole-number form. The GCD is found with the Euclidean algorithm: repeatedly replace the larger number with the remainder of dividing it by the smaller, until the remainder is 0. The decimal ratio is width รท height. Above 1 means landscape; below 1 means portrait. When you enter a new width, the height that keeps the same ratio is new width ร original height รท original width. Use it to resize images or video without distorting them.
Worked example
1920 ร 1080 (Full HD) GCD: 120 Ratio: 1920 รท 120 : 1080 รท 120 = 16 : 9 Decimal: 1.7778 New width 1280 โ height 1280 ร 1080 รท 1920 = 720 2560 ร 1080 (ultrawide) Ratio: 64 : 27 (decimal 2.3704) Often marketed as "21:9", but the exact ratio is 64:27. 1080 ร 1920 (phone in portrait) โ 9 : 16
Things to be aware of
- Monitor labels such as "21:9" are often approximate nicknames rather than exact ratios.
- Resolutions with a small GCD, such as 1366 ร 768, give large ratios like 683 : 384. The decimal ratio (about 1.78) shows it is close to 16:9.
- If the calculated height is fractional, round it to a whole number in image editors. Some video formats also require even dimensions.
FAQ
How is the aspect ratio simplified?
It's reduced to the simplest whole-number ratio by dividing both the width and height by their greatest common divisor (only when both are whole numbers).
Can I enter decimal widths and heights?
Yes, decimals work for the calculation, but the simplified ratio display only appears when both are whole numbers.
Can I work backward from a new height to find the width?
The current version only supports calculating height from a new width.