Calculators
Aspect Ratio Calculator
Simplify dimensions and resize them without changing their proportions.
About This Tool
Use width and height dimensions to find their simplest aspect ratio, then optionally resize the same shape to a different width. This is useful when preparing images, videos, thumbnails, displays, presentations, or responsive layouts where proportions need to stay consistent. The calculation runs locally and does not require uploading an image or video.
How To Use It
- Enter the original width and height as positive whole-number dimensions, such as 1920 by 1080.
- Read the simplified ratio, such as 16:9, plus the decimal width-to-height ratio.
- Optionally enter a new width to calculate the height that preserves the original proportions.
- Use the proportional dimensions when resizing content without stretching or squashing it.
Examples
1920 × 1080 video
1920 and 1080 share a greatest common divisor of 120, so dividing both values by 120 gives the familiar 16:9 aspect ratio.
Resize 1920 × 1080 to 1280 pixels wide
Keeping the 16:9 proportions, a new width of 1280 produces a proportional height of 720, giving 1280 × 720.
1080 × 1920 portrait content
Portrait dimensions of 1080 by 1920 simplify to 9:16, a common vertical video and mobile-content ratio.
Useful Notes
How the aspect ratio is simplified
The calculator finds the greatest common divisor of the original whole-number width and height, then divides both dimensions by that value. For 1920 × 1080, the divisor is 120, producing 16:9.
How proportional resizing works
To preserve the same shape, proportional height equals new width multiplied by original height and divided by original width. The result may be fractional when the requested width does not map to a whole-number height.
Aspect ratio is not resolution
Two files can share an aspect ratio while having very different resolutions. 1920 × 1080 and 1280 × 720 are both 16:9, but the first contains more pixels. Aspect ratio describes shape; resolution describes dimensions and pixel count.
Cropping and resizing are different
This calculator preserves proportions by changing dimensions together. If source content has a different ratio from a required destination, filling that destination may require cropping, padding, or another layout decision rather than proportional resizing alone.
FAQ
What does 16:9 mean?
It means the width is 16 proportional units for every 9 units of height. Many different pixel dimensions can share that same relationship.
Can I use this for portrait images?
Yes. Width can be smaller than height, so portrait dimensions such as 1080 × 1920 correctly simplify to 9:16.
Why can the calculated height contain decimals?
Some requested widths do not produce an exact whole-number height at the original ratio. If you need pixel dimensions, choose an appropriate whole-pixel rounding based on the requirements of your editor or platform.
Does this upload my image or video?
No. The calculator only uses the numeric dimensions you enter and performs the arithmetic locally in your browser.
Related Tools
Percentage Calculator
PopularFind percentages, percent change, increases, and decreases.
Basic Calculator
PopularA simple arithmetic calculator for quick results.
Data Size Converter
Convert bits, bytes, kB, MB, GB, KiB, MiB, GiB, and more.
Length Converter
PopularConvert common length and distance units.