Resize images to precise millimetre dimensions with DPI control — useful for ID photos, stamps and official forms. Free, entirely in your browser, never uploaded. No account or watermark.
Resize an image by millimeters to hit exact, precise print dimensions in your browser. This free mm image resizer converts your millimeter measurements and DPI into the correct pixel count, ideal for ID photos, business cards, stamps, labels, and any job where being a millimeter off matters. All processing is 100% client-side with WebAssembly and Canvas, so your images are never uploaded, and the tool is free with no account, watermark, or limits.
Millimeters are the go-to unit whenever small, exact print sizes are required. Passport and visa photos, business cards, name badges, product labels, stamps, and stickers are all specified in millimeters because a few millimeters of error can mean a rejected document or a misaligned print run.
Resizing by millimeters lets you enter the precise physical size a specification calls for - such as a 35 x 45 mm passport photo - and the tool works out exactly how many pixels that requires at your chosen print resolution.
There are 25.4 millimeters in one inch, so the conversion is: pixels = (millimeters / 25.4) x DPI. To reverse it: millimeters = (pixels / DPI) x 25.4. DPI (dots per inch, equivalent to pixels per inch) determines how many pixels fill each inch of print, and therefore how sharp small prints look.
For small, close-up prints like ID photos and cards, 300 DPI is the standard and 600 DPI can be used for very fine detail. Enter your millimeter dimensions, pick a DPI, and the resizer calculates the exact pixel size.
Small-format print jobs are almost always defined in millimeters. Use these standard targets and set 300 DPI (or higher) for crisp results.
Locking the aspect ratio keeps your image in proportion as you set millimeter dimensions, so faces and graphics are not distorted. For ID photos, however, the specification usually demands an exact ratio (like 35 x 45 mm) that may not match your original.
In that case, resize with the ratio locked so the subject stays natural, then crop to the exact millimeter frame required, rather than stretching the image to force both dimensions. This keeps the person or product looking correct while still meeting the precise size.
Even though millimeter prints are small, they are often viewed up close, so resolution still matters. Make sure your original has at least as many pixels as the calculated target; a 35 x 45 mm photo at 300 DPI only needs about 413 x 531 pixels, which most cameras and phones easily exceed.
Downscaling a large photo down to a small millimeter size produces excellent, sharp results. Problems only appear if you start from an already tiny image and try to enlarge it, so use the biggest, clearest source you have.
The millimeter-to-pixel math and the resize both run locally in your browser, so your photos - including sensitive ID images - are never uploaded and never stored on a server. The tool works offline after it loads, with no account, no watermark, and no limit on how many images you process.
A 35 x 45 mm image at 300 DPI is 413 x 531 pixels. The formula is pixels = (mm / 25.4) x DPI, so width = (35 / 25.4) x 300 = 413 px and height = (45 / 25.4) x 300 = 531 px.
Use pixels = (millimeters / 25.4) x DPI. Divide the millimeters by 25.4 to get inches, then multiply by your DPI. The mm resizer performs this automatically when you enter your size and DPI.
Open the MM resizer, enter 35 mm width and 45 mm height, set DPI to 300, and download. That yields about 413 x 531 pixels. Resize with the ratio locked and crop so the face stays in proportion and meets the passport frame.
A standard 85 x 55 mm business card at 300 DPI is about 1004 x 650 pixels. At 600 DPI for finer print it would be about 2008 x 1299 pixels.
Use millimeters = (pixels / DPI) x 25.4. For example, a 413-pixel-wide image at 300 DPI is (413 / 300) x 25.4 = about 35 mm. The physical size depends on the DPI you print at.
Use 300 DPI for standard small prints like ID photos and business cards. For very fine detail viewed extremely close, 600 DPI gives extra sharpness at the cost of a larger pixel dimension.
Yes. Keep the aspect-ratio lock on so the image stays in proportion, then crop to the exact millimeter frame you need. This meets the precise size without stretching faces or graphics.
No. All conversion and resizing happens in your browser using WebAssembly and Canvas, so images - including ID photos - never leave your device. The tool also works offline once loaded.
Yes. It is completely free with no account, no watermark, and no limit on how many images you resize.
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