How to resize image in cm
- Choose your photo.
- Make sure the unit says Centimetres (or switch to millimetres).
- Untick "Keep aspect ratio" if you need an exact shape like 3.5 × 4.5 cm.
- Choose 300 DPI for printing, then tap Resize image.
How cm becomes pixels
Pixels = centimetres ÷ 2.54 × DPI. For example, 5 cm at 300 DPI is 5 ÷ 2.54 × 300 = 591 pixels. The tool does this math for you and also writes the DPI into the JPG so printers and portals read the right physical size.
Common sizes in cm
| Use | Size |
|---|---|
| Passport photo (Pakistan, India, UK, EU) | 3.5 × 4.5 cm |
| Stamp-size photo | 2 × 2.5 cm |
| Signature box on many forms | 3.5 × 1.5 cm |
| Postcard | 10 × 15 cm |
Is it safe to upload my photo?
Your image is never uploaded. ResizeKB processes files inside your own browser using the same technology that draws images on web pages, so the photo never leaves your phone or computer. That matters for documents like passport photos, ID scans and signatures. You can even disconnect from the internet after the page loads and the tool keeps working.
Frequently asked questions
What DPI should I choose?
300 DPI for printing photos. Many online forms ask for 200 DPI; if yours doesn't say, 300 is safe.
Can I enter millimetres?
Yes. Switch the unit to millimetres, for example 35 × 45 mm.
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Last updated 2026-10-27