What is Crop Size Calculator?
Cropping to a target ratio means keeping the largest rectangle of that shape that fits inside the original image. If the original is wider than the target, the crop keeps the full height and trims the sides; if it is taller, it keeps the full width and trims the top and bottom. This calculator gives you the exact pixel dimensions of that centred crop and how many pixels are lost on each edge, so you can check whether your subject survives the trim before you open an editor. It is pure maths - the image never leaves your device.
Common Uses for Crop Size Calculator
- Crop a 3:2 DSLR photo to 4:5 for an Instagram portrait post
- Turn a portrait photo landscape for a YouTube thumbnail check
- Prepare 8×10 prints from a 3:2 original without guessing
- See how much headroom a 9:16 vertical crop from 16:9 footage needs
The fitting rule
Compare the shape of the original with the target. Original wider: the target rectangle spans the full height, and its width equals height × target ratio - the difference in widths is trimmed equally from the left and right. Original taller: mirror logic, trimming top and bottom. That is the whole algorithm, and it is the same one editors use when you lock a crop to a ratio.
Common print and social crops
From a landscape 3:2 original (6000×4000): cropping to 1:1 trims 33% of the width; to 8×10 (5:4) trims 17% of the width; to 4:5 portrait trims 47% of the width - which is exactly why portrait work is shot vertically in camera; and to 16:9 trims 16% of the height. Running these through the calculator before shooting or editing tells you how much safe margin to leave around your subject - the reason studio photographers leave headroom is exactly this arithmetic.