FREE WEB TOOL

DPI / pixel size calculator

Convert physical print size and DPI into required pixel dimensions.

Use tool

Width (mm)Height (mm)DPI

How to use it

Convert a physical print size in millimeters plus DPI into the pixel dimensions required for that print size.

Enter width and height in millimeters.
Enter a positive DPI value.
Select Calculate to get the required pixel width and height.

Formula: mm ÷ 25.4 × DPI
Rounding: Each pixel dimension is rounded up
Inputs: Positive width, height and DPI
Output: width × height pixels

A5 at 350 DPI is about 2,040 × 2,894 px

For 148 × 210 mm at 350 DPI, the raw values are about 2039.37 × 2893.70, so the tool rounds upward to 2040 × 2894 px.

DPI here is a print-density planning value. Changing only metadata does not create missing image detail; the source still needs enough actual pixels.

25.4 mm equals one inch

DPI is dots per inch, so millimeters are first converted to inches before multiplying by the requested density.

The tool rounds upward rather than to the nearest pixel

Using ceiling avoids returning a dimension fractionally below the requested physical density.

More DPI means more required pixels

Keeping print size fixed while doubling DPI approximately doubles each pixel dimension and quadruples total pixel count.

Printer behavior can still differ

Scaling options in print dialogs, bleed, trimming and device-specific rasterization are outside this calculation. Use the result as the source-image target size.

Related references: Paper sizes · DPI, PPI & px · Aspect ratios