A pixel is not a length on its own
Asking how many centimetres 413 pixels is only has an answer once you fix a DPI. At 300 DPI it is 3.5cm; at 96 DPI it is about 10.9cm. That is why the DPI comes first here.
| Use | Typical DPI |
|---|---|
| Web and CSS | 96 |
| Screen preview | 72 |
| Standard print | 300 |
| High-quality print | 600 |
The formulas
- Pixels to millimetres:
mm = px ÷ DPI × 25.4 - Millimetres to pixels:
px = mm ÷ 25.4 × DPI
A 35mm passport photo at 300 DPI comes out as 413px through exactly this.
Common specs in pixels
Passport photos, business cards and paper sizes are listed with their pixel dimensions at the DPI you picked, ready to use as a canvas size.
For everyday units such as length and weight use the unit converter; to save a photo at an official spec use the passport photo resizer.