Digital Image Resolution Unit Converter

Convert pixel density among pixels per millimeter (px/mm), pixels per inch (PPI) and pixels per centimeter (px/cm). The tool does not convert printer dots per inch (DPI).

Enter your values in the calculator fields to get an instant result.

Calculator guide

Convert pixel density among pixels per millimeter (px/mm), pixels per inch (PPI) and pixels per centimeter (px/cm). The tool does not convert printer dots per inch (DPI).

Formula or method

Output = input × source factor ÷ destination factor. Since 1 inch = 25.4 mm, 1 px/mm = 25.4 PPI and 1 px/cm = 2.54 PPI.

How to use this calculator

  1. Enter the density value. The initial amount is 1.
  2. Choose From unit and To unit. Available choices are px/mm, pixels per inch (PPI) and px/cm.
  3. Read Converted value with its destination unit; no image file or pixel dimensions are entered or changed.

Worked example

Select pixels per millimeter (px/mm) → pixels per inch (PPI), then enter 10: 10 × 25.4 = 254 PPI. The image’s pixel count remains unchanged.

Understanding the result

PPI describes image pixels per physical inch. DPI describes physical printer dots per inch; the two are related in a print workflow but are not interchangeable units without details of the printer and rasterization.

Limitations and assumptions

  • Only px/mm, PPI and px/cm are selectable. Printer DPI, line screens, image dimensions, resizing, resampling and print layout are not calculated.
  • A print dimension also needs the image pixel dimensions: inches = pixels ÷ PPI. Converting a density value alone does not determine print size or image quality.
  • Displayed values are rounded to at most eight fractional digits; the conversion does not add image detail or measurement precision.

Frequently asked questions

Does this convert PPI to printer DPI?

No. PPI counts image pixels per inch; DPI counts printer dots per inch. This converter offers only pixel-density units.

Does changing the unit resize the image?

No. No image is uploaded or altered, and total pixel dimensions are not an input.

How do I find print width?

Divide the image’s pixel width by its PPI. This converter does not take pixel dimensions or calculate a print layout.

Sources

Educational and planning information only. Sources are attributed background or formula references, not endorsements. Verify consequential decisions with an appropriate qualified professional.