Printing passport photos so they come out the right size
You can crop a photo to exactly 35 × 45 mm, print it, measure it with a ruler, and find it is 41 mm wide. The crop was right. The printing was wrong. Here is why that happens and how to stop it.
Pixels have no size
A digital image is a grid of pixels. On its own, a grid of 600 × 750 pixels has no physical size at all — it is just a count. It becomes a physical size only when something decides how densely to lay those pixels down on paper.
That density is DPI: dots per inch. The same 600 × 750 image is:
- 2 × 2.5 inches at 300 DPI
- 8.3 × 10.4 inches at 72 DPI
Same file, same pixels, wildly different prints.
Where the size actually lives
Image files can carry a field recording their intended DPI. JPEG stores it in a
header called the JFIF segment; PNG stores it in a chunk called pHYs. Print
software reads that field to work out how big the image should be.
The catch: when a web page creates an image, the browser writes no DPI information at all. So a photo cropped in the browser to precisely the right millimetre size arrives at your printer as a bare pixel grid with no instructions, and the printer scales it to whatever seems reasonable.
This is why so many browser-based photo tools produce the wrong print size, and it is why our editor writes the correct DPI into every file it generates. It is not a detail you should have to think about.
The other half: your print dialog
Even a correctly tagged file gets ruined by the wrong print setting. Almost every print dialog defaults to something like "Fit to page" or "Scale to fit", which overrides the file's own size and stretches it to the paper.
Print at "Actual size", "100%", or "Original size". Turn off any fit-to-page, shrink-to-fit or auto-rotate option. In most dialogs this is one checkbox, and it is the difference between a usable photo and a wasted sheet.
Also set the correct paper size, and use photo paper — most authorities require photos printed on proper photographic paper, and Canada does not accept home printing at all.
Use a print sheet
Rather than printing one small photo in the middle of a sheet, print several tiled together. Our print sheet option lays copies out on a 6 × 4 inch photo print, A4, or US Letter with cut guides on the seams.
A 6 × 4 print at 300 DPI is 1800 × 1200 pixels, and six 2 × 2 inch US passport photos fill it exactly — three across, two down. That is the standard layout every photo lab uses, which is why a 6 × 4 is the cheapest way to get passport photos printed: hand the file to any print counter and cut them up yourself.
Verify with a ruler
Print one, measure it. This takes ten seconds and is the only check that actually proves the whole chain worked:
- The photo edges should measure the spec size — 35 × 45 mm, or 51 × 51 mm, or whatever your country requires.
- Chin to the top of your head should land inside the permitted range.
If the outer dimensions are wrong, it is nearly always the print dialog scaling. Go back and set it to actual size.
If you are submitting digitally
Many countries now accept a digital upload, in which case DPI is irrelevant and only the pixel count matters — but the minimums are real. The UK wants at least 600 × 750 pixels, the US at least 600 × 600.
Worth knowing: 35 × 45 mm at 300 DPI is only 413 × 531 pixels, which is below the UK's own digital minimum. A tool that renders everything at a flat 300 DPI produces a UK photo that fails the upload check. Ours resolves the resolution upward so the print size and the pixel floor are both satisfied — a UK photo comes out 601 × 773 at 436 DPI, which measures 35 × 45 mm on paper and clears the 600 × 750 requirement on screen.
Make a passport photo — free, and your photo never leaves your device.