How is the largest crop calculated?

The tool compares your target ratio to the source ratio. If the target is wider it keeps the full source width and trims the height; if the target is taller or narrower it keeps the full height and trims the width. This guarantees the biggest possible crop of that ratio fits inside the original, centred.

Does cropping reduce my megapixels?

Yes. Cropping discards pixels, so the output always has fewer megapixels than the source. The tool shows both the original and cropped megapixel counts so you can confirm you still have enough resolution for your intended print or display size.

Why do I lose so many pixels going to a wide ratio?

Reshaping a 3:2 photo into 16:9 or 21:9 means cutting away the top and bottom, and a 21:9 cinema crop from a 3:2 frame can discard around a third of the image. The wider the target relative to the source, the more vertical pixels are removed.

Can this tool add pixels or upscale?

No. Cropping only ever keeps or discards captured pixels — it cannot invent new detail. If you need more output pixels than the crop provides, that requires separate upscaling software, which is a different operation with its own quality trade-offs.

What resolution do I need for a print?

A common target is 300 pixels per inch, so a 6 by 4 inch print needs about 1800 by 1200 pixels and a 12 by 8 inch print about 3600 by 2400. Check the cropped megapixel count against your print size to confirm you stay above roughly 240 to 300 ppi.

Photo Aspect Ratio & Crop Calculator

When you reshape a photo to a new aspect ratio — square for social, 16:9 for a slideshow, 9:16 for vertical video — you trade away pixels. This calculator shows exactly how big the cropped image will be, how many megapixels survive and what percentage of the original you lose, before you commit the crop in your editor.

How it works

Given a source W × H and a target ratio aw:ah, the tool finds the largest rectangle of that ratio that fits inside the source, centred. It compares the two ratios:

target ratio = aw / ah
source ratio = W / H

If the target is wider than the source, the crop is limited by width — it keeps the full width and trims the height:

crop width  = W
crop height = round(W / target ratio)

If the target is taller or narrower, it keeps the full height and trims the width:

crop height = H
crop width  = round(H × target ratio)

Megapixels are width × height ÷ 1,000,000, and pixels lost is the percentage difference between the source area and the crop area.

Worked example

A 24-megapixel 3:2 file is 6000 × 4000. Cropping to 16:9 keeps the full 6000-pixel width and reduces the height to 6000 ÷ (16/9) = 3375. The result is 6000 × 3375 ≈ 20.3 MP, losing about 15.6% of the original pixels — all from the top and bottom of the frame.

Cropping the same file to 1:1 instead is limited by the 4000-pixel height, giving 4000 × 4000 = 16 MP and losing a third of the pixels from the sides.

Tips and notes

Compose with a little room around your subject when you know a tight crop is coming — you cannot recover pixels you did not capture.
For prints, aim to keep the cropped image above roughly 240 to 300 pixels per inch at your final size. The megapixel readout makes that easy to check.
Custom ratios accept any positive numbers, so you can match an unusual frame or print size exactly.