Exact geometryWhole-pixel output
How the aspect ratio crop calculator works
The calculator finds the largest rectangle with your target ratio that fits entirely inside the source dimensions. It never enlarges or stretches the source. If the source is wider than the target, pixels are removed from the left and right. If the source is taller, pixels are removed from the top and bottom.
kept area % = (crop width × crop height) ÷ (source width × source height) × 100
Crop loss is 100% minus the retained area. Because files use whole pixels, the calculated crop width or height is rounded to the nearest pixel.
Example: crop 16:9 to 9:16
A 1920×1080 landscape source converted to a centered 9:16 frame produces a 608×1080 crop after whole-pixel rounding. It removes 1,312 horizontal pixels—656 from the left and 656 from the right—and retains about 31.67% of the original area.
This large loss is why vertical versions often need manual reframing rather than an automatic center crop.
Crop vs resize vs padding
Crop
Changes the shape by removing source pixels. It fills the target frame without distortion.
Proportional resize
Changes pixel dimensions but keeps the original shape. Use the aspect ratio converter.
Padding or letterboxing
Keeps the full source and adds empty space when the source and target shapes differ.