Convert millimeters to pixels at 300 dpi: px = mm ÷ 25.4 × 300. Print-size math for metric users.
| Input | Result |
|---|---|
| 50 mm at 300 dpi | 591 px |
| 100 mm at 300 dpi | 1,181 px |
| 25 mm at 300 dpi | 295 px |
50 ÷ 25.4 × 300 ≈ 591 px. For a 50 × 50 mm print that is a 591 × 591 px image.
DPI is dots per <i>inch</i>, and 1 inch = 25.4 mm exactly. Converting mm to inches first is the whole trick.
Screen density is a separate concept (96 dpi CSS reference, or device PPI). The 300 dpi figure applies to physical printing only.