Photo Size in Pixels at 300 DPI: The CM-to-Pixel Table Indian Forms Need
Forms state photo sizes in centimetres or millimetres, editors show pixels, and portals validate both. The bridge between the two worlds is DPI: dots per inch defines how many pixels a physical size contains, and 300 DPI is the print and portal standard in India.
This guide gives the conversion arithmetic, the ready table for every common size, and the metadata detail that separates an accepted upload from a silent rejection.
The arithmetic in one line
Pixels equal centimetres divided by 2.54, multiplied by DPI. So 3.5 cm at 300 DPI is 3.5 / 2.54 x 300 = 413 pixels, and 4.5 cm becomes 531.
At 200 DPI the same 3.5 x 4.5 cm rectangle holds only 276 x 354 pixels | same physical size, fewer pixels, softer print.
- 300 DPI: print and portal standard.
- 200 DPI: some older portals and internal records.
- 96 DPI: screen default | the classic reason a phone export prints tiny.
The table people actually need
- 3.5 x 4.5 cm at 300 DPI = 413 x 531 px (SSC, most exam portals).
- 5.1 x 5.1 cm at 300 DPI = 602 x 602 px (Indian passport square).
- 2.5 x 3.0 cm at 300 DPI = 295 x 354 px (common stamp size).
- 2.0 x 2.5 cm at 300 DPI = 236 x 295 px (small stamp variants).
- 4.5 x 3.5 cm at 300 DPI = 531 x 413 px (landscape framing some state portals use).
- Signatures: 4.0 x 1.5 cm at 300 DPI = 472 x 177 px, and 3.5 x 1.5 cm = 413 x 177 px.
Why metadata, not pixels, decides acceptance
Two files can hold identical pixel grids and behave differently at upload: the one whose JFIF header stamps 300 DPI passes a density check, the one stamped 96 DPI fails it, because the portal computes physical size from header plus pixels.
Renaming, screenshotting or chat-app re-sends strip or rewrite that header. A resizer that writes true DPI restores it.
Check and fix density with a DPI converter before compression, then compress to the KB window | order matters because some compressors preserve the stamp and some do not.
Phone captures and the 96 DPI trap
Phone cameras export at screen density by default, so a perfectly framed capture arrives stamped 96 DPI and prints at triple the intended size.
The fix is metadata-only: set 300 DPI without touching pixels when the pixel grid already matches the table, or resize and stamp together when it does not.
- Rule of thumb: capture big, resize to table pixels, stamp 300 DPI, compress last.
Try it free: Convert DPI tool | runs entirely in your browser, no uploads and no signup.