Aspect Ratio Calculator Free
Calculates a width-to-height ratio, such as 16:9, from a width and height, or the missing width or height from a ratio.
Common ratios
About this tool
If the calculated length comes out as a decimal, it's rounded to a whole number; the unrounded value is shown too.
You can also copy the ratio in CSS aspect-ratio syntax.
This tool runs entirely in your browser. Nothing you enter is sent to our server.
When to use it
Useful for resizing an image or video to a different size while keeping the same ratio, such as 16:9 or 4:3, by calculating the matching width or height.
Also useful for checking which common ratio a resolution, such as 1366×768, is closest to.
How to use
- Choose "Width & height → ratio," "Ratio & width → height," or "Ratio & height → width."
- Enter the numbers, or pick one of the "Common ratios" buttons to fill in the ratio field.
How the ratio is simplified
The width and height are divided by their greatest common divisor to get the simplest ratio, so 1920×1080 becomes 16:9. When the result is within 1% of a common ratio, that's noted too, such as "about 16:9."
FAQ
- What is the CSS aspect-ratio property?
- It's a CSS property that sets an element's width-to-height ratio. For example, aspect-ratio: 16 / 9; makes the height follow the width at a 16:9 ratio.
- Is what I enter sent anywhere?
- No. The calculation happens entirely in your browser.