Resize image in mm
Some forms, visa checklists and photo labs give sizes in millimetres. Type them here and the image is resized to the matching pixel count at your chosen DPI.
JPG, PNG, WebP or HEIC, up to 25 MB
Processed on your device. Never uploaded.
Settings
The other side follows so the picture is not stretched.
Used to turn cm, mm or inches into pixels, and written into the file. 200 if your notice gives none.
Leave empty for no limit.
About this tool and size
Millimetres, inches and DPI
One inch is 25.4 millimetres, and the DPI says how many pixels fit in that inch. So pixels = mm ÷ 25.4 × DPI. Small millimetre sizes are sensitive to this: a 20 mm side is 157 px at 200 DPI but 236 px at 300 DPI. When a notice gives a size in mm and also a DPI, use both exactly; when it gives no DPI, 200 is the safe default for uploads.
Millimetre sizes appear mostly for photos: 35 × 45 mm, 51 × 51 mm (2 × 2 inch) for some visa applications, and small stamp prints. For signatures, notices tend to use centimetres instead.
Printing at the right size
If you will print the result, choose 300 DPI and print at 100% (actual size), never "fit to page". To place several copies on one sheet with cut lines, the photo sheet tool does the layout for you.
How to use it
- Choose the image. Open a photo from your gallery or camera. Its present size is shown in mm.
- Enter millimetres. Type the width and height in mm. Switch the aspect lock off when both numbers are fixed.
- Pick the DPI. Millimetres only become pixels through the DPI. 200 suits uploads; 300 suits printing.
- Download. Optionally cap the KB, then save the file once every check passes.
Questions
How many pixels is 1 mm?
At 200 DPI one millimetre is about 7.87 pixels, and at 300 DPI about 11.81 pixels, because an inch is 25.4 mm. The tool multiplies and rounds to whole pixels.
What is 35 × 45 mm in pixels?
It is 276 × 354 px at 200 DPI and 413 × 531 px at 300 DPI. That is the same as 3.5 × 4.5 cm, the common passport-size photo on Indian forms.
What is 51 × 51 mm in pixels?
At 200 DPI it is 402 × 402 px; at 300 DPI it is 602 × 602 px. A 2 × 2 inch photo at 300 DPI is exactly 600 × 600 px, the tiny difference coming from rounding 2 inches to 51 mm.
Does it work without internet?
Yes, after your first visit the page works offline, and images are processed on your device either way.