This tool matches your camera’s native aspect ratio against the print sizes a lab actually offers, so you know in advance which ones fill the paper edge to edge and which will crop your image. No more surprise white borders or a head cropped off at the print counter.
How it works
Every image and every print size has an aspect ratio — the long edge divided
by the short edge. A 3:2 sensor has a ratio of 1.5; a 6x4 inch print is also
1.5. When the two match, the image fills the paper perfectly.
When they differ, filling the print means cropping the longer dimension of the image. The tool computes the crop like this:
imgRatio = sensor long / sensor short
printRatio = print long / print shortIt orients the print to best fit the image, then the fraction of the image’s long edge lost is:
crop = 1 - (min(imgRatio, printRatio) / max(imgRatio, printRatio))A crop of 0 is a perfect match. A 3:2 image on a 7:5 (1.4) print loses about
1 - 1.4/1.5 = 6.7% of its long edge.
Why ratios differ — sensor by sensor
3:2 sensors (most full-frame, APS-C DSLRs and mirrorless cameras) inherit the ratio from 35 mm film. These cameras match 6x4 in, 9x6 in, 12x8 in, and 18x12 in perfectly. The popular 7x5 in print is a 7:5 ratio (1.4), so a 3:2 shot loses about 6.7% of its long edge — typically a thin strip from each side, which is usually fine unless your subject fills the frame tightly.
4:3 sensors (Micro Four Thirds cameras, many compact cameras, and some smartphones) sit between 3:2 and the square. They match 8x6 in exactly and come close to A-series ISO paper, which uses a ratio of approximately 1.414 (the square root of 2). The 6x4 in print is more of a mismatch for these sensors than for 3:2 cameras.
16:9 sensors or crop modes are designed for video, not prints. The ratio (approximately 1.78) does not correspond to any standard photo paper size. Printing a 16:9 image at 10x8 or 7x5 always crops significantly — roughly 10–25% of the long edge, depending on the print size chosen.
1:1 (square) images match square prints perfectly and crop noticeably on every rectangular size. If you shoot in square mode, commit to square prints or crop afterward for standard sizes.
Common print sizes ranked by crop for a 3:2 sensor
| Print size | Ratio | Crop from 3:2 image |
|---|---|---|
| 6x4 in | 3:2 = 1.50 | 0% — perfect match |
| 9x6 in | 3:2 = 1.50 | 0% — perfect match |
| 12x8 in | 3:2 = 1.50 | 0% — perfect match |
| 7x5 in | 7:5 = 1.40 | ~6.7% |
| 10x8 in | 5:4 = 1.25 | ~16.7% |
| A4 (landscape) | ~1.41 | ~6% |
Shooting with print cropping in mind
If you know before a shoot that you will be printing at a size that does not match your sensor ratio, you can compensate at the composition stage:
- Leave breathing room around subjects at the edges. The lab’s crop removes the frame edges, not the centre. A portrait framed tightly left-to-right will lose part of one or both shoulders when printed at 7x5.
- Use viewfinder overlays. Many cameras let you display a crop guide in the viewfinder for a different aspect ratio, so you can compose for the print size even while shooting in native ratio.
- Shoot RAW and crop intentionally in post. Rather than letting the lab decide which edge to trim, crop to your target print ratio yourself while reviewing, so you control exactly what survives.
All comparisons run locally in your browser — no images or camera data are uploaded.