51 × 51 mm passport photo (602 × 602 px)
The metric round of the two-inch square. 51 × 51 mm at 300 dpi is 602 × 602 pixels.
The spec, and why the numbers look odd
51 × 51 mm is what two inches becomes when you round to whole millimetres. It is the size printed on Indian visa and OCI checklists, and it appears on a scattering of other forms that specify a square photo in metric.
Because it is a rounding of 50.8 mm, the exact pixel count differs from the US 600 × 600: 602 instead of 600. For most portals that difference is irrelevant, but if a form is strict about pixels, use the number it names.
The head should fill roughly 70–80% of the frame, similar to the 35 × 45 rule rather than the smaller US head size.
Print size vs screen size
| Where it goes | What matters | Watch out for |
|---|---|---|
| Online upload | Pixel dimensions | Portals often re-encode and add a few KB |
| Printed at a kiosk | Physical mm at 300 dpi | Choosing 'fit to page' silently rescales it |
| Home printer | Physical mm at 300 dpi | Set scaling to 100%, not 'shrink to fit' |
| Scanned and re-submitted | 300 dpi | Scanning below 300 dpi softens the face |
Questions
Is 51 × 51 mm the same as 2 × 2 inches?
Practically yes — 2 inches is 50.8 mm. The pixel counts differ slightly (602 vs 600).
Which should I pick for a US passport?
The 2 × 2 inch spec (600 × 600). It is what the US form expects.
Does the background need to be white?
Yes for Indian visa photos — plain white or very light, with no shadow.
Can I use the print sheet abroad?
4 × 6 inches is a standard photo print size in most countries. In metric countries ask for 10 × 15 cm, which is the same thing.