Aspect-Ratio & Crop Calculator

What the calculator measures

This tool fits the largest rectangle of your chosen aspect ratio inside the source frame. It assumes no padding and no distortion. If the source is wider than the target, it removes material at the sides. If the source is taller than the target, it removes material above and below.

Worked example: 4K landscape to vertical

A 3840 × 2160 landscape source cropped to 9:16 retains an ideal 1215 × 2160 rectangle. That is 31.640625% of the original image area. A centred crop removes more than two thirds of the width, so a subject near an edge can disappear even though the export remains sharp.

Ideal geometry versus encoder pixels

Some results include fractional pixels. A real editor must round to an appropriate pixel grid, and some codecs require even dimensions. Treat the output as geometric planning, then choose supported export dimensions and inspect the actual rendered frame.

Crop, pad or reframe?

Cropping fills the destination but removes image area. Padding keeps the full frame with space around it. Reframing moves the crop window to follow the chosen subject. This calculator does not detect or track subjects; it only shows the available geometry.

Check the whole shot

A subject that fits at the start may leave the frame later. Scrub the entire clip and inspect changes in movement, horizon and composition. When a wide aerial reveal needs the full landscape, a separate landscape edit may communicate more than forcing it into a vertical version.

Frequently asked questions

Does a crop calculator increase resolution?

No. It measures a rectangle inside the original image. Upscaling to a larger output does not create original camera detail.

What if I want black bars instead?

That is a fit or contain treatment, not a fill crop. The tool deliberately calculates cropping without padding.

Formulas and examples reviewed on 26 October 2026. Planning estimates, not measurements of your footage or equipment.