Resize Image in mm

Photo rules, card printers and paper sizes are written in millimeters, while the file on your phone only knows pixels. Enter the millimeter size and a DPI here, and the image is cropped to that shape, sized to the matching pixel count and tagged so it prints at the size you typed.

or drop JPG, JPEG, JFIF … files here ·

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How to use this tool

1
Add the photo or scan
Upload up to 20 JPG, PNG, HEIC, WebP or TIFF files. Every file in the batch gets the same size.
2
Enter millimeters and DPI
Unit is on mm with Width 35 and Height 45, the most requested photo size. Replace them with your numbers and set DPI under Fit & print; it starts at 300.
3
Resize and check the pixels
Press Resize and download. At 300 DPI the default gives 413 × 531 px; check that figure in your file's properties before you upload or print.

Resize image in mm: what happens to the file

A millimeter size is a print instruction, not a property of the file. The image is a grid of pixels plus a DPI tag, the number of pixels that should fill one inch of paper. So the tool needs two inputs: the millimeters you want on paper and the DPI.

With both set, the steps are fixed. The millimeters are converted to pixels, the photo is scaled until it covers that frame, the overflow is trimmed around the subject, and the DPI is written into the file so Word, a print shop or a photo kiosk places it at the right physical size.

Common sizes in millimeters and their pixel counts

Size	Pixels	cm	in	DPI	Fits
35 × 45 mm	413 × 531	3.5 × 4.5	1.38 × 1.77	300	UK passport, Schengen visa, many exam forms
50.8 × 50.8 mm	600 × 600	5.08 × 5.08	2 × 2	300	US passport and visa photo
85.6 × 54 mm	1011 × 638	8.56 × 5.4	3.37 × 2.13	300	ID-1 card: bank, ID and membership cards
100 × 150 mm	1181 × 1772	10 × 15	3.94 × 5.91	300	Standard photo print, close to 4 × 6 in
105 × 148 mm	1240 × 1748	10.5 × 14.8	4.13 × 5.83	300	A6 postcard and flyer
210 × 297 mm	2480 × 3508	21 × 29.7	8.27 × 11.69	300	A4 page, full bleed

DPI, the number that links millimeters to pixels

DPI (dots per inch)PPI · pixels per inch · print resolution: The count of pixels a printer lays down across one inch, 25.4 mm, of paper. It is stored in the image file as a tag. At 300 DPI each millimeter holds about 11.8 pixels; at 150 DPI about 5.9.

Getting a millimeter size right the first time

Most paper sizes you meet outside North America come from ISO 216, the A series, which is defined in millimeters: A4 is 210 × 297 mm and every smaller size halves the one above it. Photo rules follow the same habit, so a millimeter field is often the precise version of an instruction someone else rounded to centimeters or inches.

Two checks prevent most rejected prints and uploads. Start from a source with more pixels than the target, since a 35 × 45 mm photo at 300 DPI needs 413 × 531 px and a small crop from a group shot may not have them; tick Never enlarge if you prefer to keep the original detail. And when a form adds a KB limit to the millimeter size, tick Limit file size too, or read passport size photo in cm, inches and pixels for the full routine.

Resizing images in millimeters: FAQ

How do I convert millimeters to pixels?

Divide the millimeters by 25.4 to get inches, then multiply by the DPI. 35 mm at 300 DPI is 35 ÷ 25.4 × 300 = 413 px. The 25.4 is exact: the inch has been defined as 25.4 mm since the international yard and pound agreement of 1959.

Why is 35 × 45 mm the default here?

It is the most common photo size in official rules. GOV.UK asks for 35 mm wide by 45 mm high for UK passport photos, Schengen visa applications use the same frame, and many other countries copy it. If you need the full photo workflow with a head-size guide, the passport photo maker handles it.

What DPI should I use with a millimeter size?

300 DPI for anything printed at photo quality, including ID photos and cards. Online forms that only state millimeters are usually happy with 200 to 300 DPI. Fewer dots per inch give a smaller file but a softer face if someone prints it.

Is resizing in mm different from resizing in cm?

Only in the unit you type. 35 mm and 3.5 cm produce the same 413 px at 300 DPI. Millimeters avoid decimals, which is why print specs prefer them; if your instructions are in centimeters, resize image in cm opens with that unit set.

Can I make an image the size of a bank card?

Yes. The standard card format, ID-1 in ISO/IEC 7810, is 85.60 × 53.98 mm. Enter 85.6 and 54 with DPI 300 and you get about 1011 × 638 px, ready for a card printer template or a membership card design.

My printed photo came out a few millimeters off. Why?

The printer's own setting won, usually Fit to page or Borderless, which scales the image. Print at 100% or actual size; the file itself carries the size you entered.