Image Resizer PCHow cm and DPI become pixels
Images are stored in pixels, but print and passport rules are usually given in centimetres. The link between them is DPI (dots per inch). The formula is simple: pixels = cm ÷ 2.54 × DPI. You don't have to do the arithmetic — type the cm and the DPI and the app fills in the pixels.
For example, a 3.5 × 4.5 cm passport photo at 300 DPI works out to about 413 × 531 pixels. Lower the DPI and you get fewer pixels for the same physical size.
- 3.5 × 4.5 cm @ 300 DPI ≈ 413 × 531 px (passport/visa)
- 2 × 2 in @ 300 DPI = 600 × 600 px (US-style photo)
- Formula: pixels = cm ÷ 2.54 × DPI
- 300 DPI is the usual standard for print
cm vs pixels — which should you use?
Use centimetres when something will be printed or when a photo spec is physical — passport booths, visa forms and photo labs all talk in cm (or inches) plus a DPI. Use pixels when the requirement is purely on-screen, like an exam portal that asks for 200 × 230 px.
If a form gives you both a cm size and a pixel size, they should agree at the stated DPI. When in doubt, match the pixel number the portal prints — that's what it actually checks.
Passport and print sizing tips
For a standard 3.5 × 4.5 cm passport or visa photo, set cm mode to 3.5 × 4.5 and DPI to 300. Keep the aspect ratio or center-crop so your face isn't stretched, and position the crop so the head sits where the guidelines want it.
Many portals also cap the file weight, not just the size. After setting the cm dimensions you can give the app a KB target too — for instance DS-160 allows up to about 240 KB and OCI around 500 KB, but always check your specific portal. One honest note: forcing a large print size into a very small KB cap will soften the image, so don't set the KB target lower than the portal actually requires.