Crop Dimension Calculator
Calculate the largest crop of an image that fits a target aspect ratio, so you can crop to 16:9, 1:1 or any ratio without distortion.
Last reviewed by the Radiatus Cloud team
Calculate the largest crop that fits a target aspect ratio.
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Calculate a crop to a target ratio
Cropping an image to a specific aspect ratio, such as a square for a profile picture or sixteen-by-nine for a video thumbnail, means trimming the excess from the longer dimension. This calculator finds the largest region of your image that matches a target ratio, centred within the original. For a nineteen-twenty by twelve-hundred image cropped to sixteen-by-nine, it keeps the full width and trims the height to ten-eighty, removing sixty pixels from the top and bottom.
It tells you the resulting crop size, how much to trim from each side, and what fraction of the pixels you keep.
Cropping without distortion
Cropping, unlike resizing, changes which part of the image is shown rather than squashing it, so the subject keeps its natural proportions. Calculating the crop box in advance helps when preparing images for layouts and platforms that require a fixed aspect ratio. Centring the crop is the common default, though you may wish to shift it to keep the subject in frame.
If the image is already in the target ratio, no cropping is needed and the full image is kept. All calculation happens locally in your browser.
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Frequently Asked Questions
How is the crop size calculated?
The tool finds the largest rectangle of the target ratio that fits inside the original, trimming only the longer dimension.
Does cropping distort the image?
No. Cropping removes part of the image rather than stretching it, so the remaining subject keeps its natural proportions.
Where is the crop taken from?
This tool centres the crop, trimming equally from opposite sides. You can shift it if you need to keep a specific subject in frame.
What if my image is already the right ratio?
Then no cropping is needed, and the calculator keeps the full image, showing that nothing is trimmed.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Enter the original size and target aspect ratio.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
Related Tools
EXIF Viewer
ImageExtract hidden EXIF data (Camera, GPS, Settings) from images.
Favicon Generator
ImageGenerate favicons and app icons at every required size from one source image, with the exact HTML to reference them.
Placeholder Image Generator
ImageGenerate placeholder images at any size with custom colours and label text. Produced in your browser as downloadable files, no external hotlinking.