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 portals, 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
Example Photo Dimension Calculations
These are illustrative examples for understanding DPI and pixel conversion. Actual application requirements vary. Always verify the latest dimensions, DPI, file size and format on the relevant official portal.
| Document / Portal | Physical Size | Standard DPI | Required Pixel Resolution |
|---|---|---|---|
| Example A (e.g., Standard Format) | 3.5 cm × 4.5 cm | 300 DPI | 413 × 531 px |
| Example B (e.g., 2x2 inch Format) | 2.0 in × 2.0 in (51x51 mm) | 300 DPI | 600 × 600 px |
| Example C (e.g., European Format) | 3.5 cm × 4.5 cm | 300 DPI | 413 × 531 px |
| Example Signature Scan | 3.5 cm × 1.5 cm | 200 DPI | 275 × 118 px (or 140x60 px) |