Demystifying DPI (Dots Per Inch)
DPI (Dots Per Inch) or PPI (Pixels Per Inch) defines the density of pixels when a digital image is rendered onto a physical medium (such as paper or photographic film).
Digital screens do not have fixed physical inches — a 1000 × 1000 pixel image simply occupies 1000 screen pixels regardless of whether its internal DPI metadata header is set to 72, 96, or 300. However, when printing or submitting to official passport agencies, DPI dictates how large that image will appear in real life.
The Universal DPI Conversion Formulas
To Convert Inches to Pixels:
Pixels = Inches × DPI
To Convert Centimeters to Pixels:
Pixels = (Centimeters / 2.54) × DPI
To Convert Millimeters to Pixels:
Pixels = (Millimeters / 25.4) × DPI
Standard Official Photo Dimension Chart
| Document / Portal | Physical Size | Standard DPI | Required Pixel Resolution |
|---|---|---|---|
| Indian Passport / SSC / UPSC | 3.5 cm × 4.5 cm | 300 DPI | 413 × 531 px |
| US Visa / US Passport (2x2 in) | 2.0 in × 2.0 in (51x51 mm) | 300 DPI | 600 × 600 px |
| Schengen European Visa | 3.5 cm × 4.5 cm | 300 DPI | 413 × 531 px |
| Government Signature Scan | 3.5 cm × 1.5 cm | 200 DPI | 275 × 118 px (or 140x60 px) |