Image aspect ratio calculator
Reduce image width and height to an exact aspect ratio and calculate a matching height for a new width. Whole-pixel rounding is shown explicitly.
Your input and results stay in this browser.
Keep proportions when preparing an image
Enter the original width and height in whole pixels. The greatest common divisor reduces 1920 × 1080 to 16:9. Choose a new width, such as 1200 pixels, to obtain the matching height of 675 pixels. A ratio is not a file-size limit: a 16:9 image can still be too large in bytes for an upload.
Rounding and image editing
The matching height is rounded to the nearest whole pixel, so an exact ratio may vary slightly for small dimensions. This calculator creates numbers, not a resized image. Use the resize tool to create a new file or the crop tool when the destination requires a different shape. Widths and heights must be positive integers up to one million.
Workflow and result checks
- Enter the original pixel dimensions.
- Choose the desired new width.
- Calculate and apply the values in the resize tool.
Questions about this tool
Does this resize my image?
No. The calculator only returns dimensions. Open the resize tool to create an image copy.
Why is the new height rounded?
Raster images need whole pixels; arbitrary proportions can produce fractional heights.