Aspect Ratio Crop Calculator
Find the largest crop of a given width and height that fits a target aspect ratio, with the pixels trimmed from each side.
How it works
If width÷height > ratio: crop width = height × ratio · else crop height = width ÷ ratio
Fitting an image to a new aspect ratio means keeping whichever dimension already fits and trimming the other. If the original is wider than the target ratio you crop the sides; if it is taller you crop the top and bottom. Centering the crop splits the trimmed pixels evenly, and the kept-area percentage tells you how much of the original survives.
Worked example
A 4000×3000 photo (ratio 1.333) cropped to 16:9 (ratio 1.778) is wider-than-tall relative to the target — no, it is narrower, so height is trimmed: crop width stays 4000, crop height = 4000 ÷ 1.778 = 2250 px. That trims 750 px of height, 375 from top and bottom, keeping 75% of the image.
Sources: Aspect ratio (image) — Wikipedia
Frequently asked questions
Why can’t I keep the whole image?
Unless the original already matches the target ratio, some pixels must go. Reshaping without cropping would stretch the picture and distort everything in it, so cropping trades a little content for correct proportions.
Does this upscale the image?
No. It only crops, so the result is never larger than the original in either dimension. If you need more pixels than the crop provides, you would resample afterwards, which softens detail.
How do I crop off-center?
This tool centers the crop and splits the trim evenly. To favour one side, take the total trim it reports and move more of it to the opposite edge — the crop size stays the same, only its position changes.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.