Conversion method
Spatial sampling density only. Pixels and printer dots are different physical concepts even when the numerical density matches. This does not calculate total image pixels or screen scaling.
px/cm = x × 0.39370078740157477
10 ppi = 3.937008 px/cm.
| ppi | px/cm |
|---|---|
| 1 | 0.393701 |
| 5 | 1.968504 |
| 10 | 3.937008 |
| 25 | 9.84252 |
| 50 | 19.685039 |
| 100 | 39.370079 |
Unit definitions and sources
Spatial sampling density only. Pixels and printer dots are different physical concepts even when the numerical density matches. This does not calculate total image pixels or screen scaling.
| Unit and system | Use | Definition | Relationship |
|---|---|---|---|
| Pixel per inch (ppi); si | Common units | Pixel per inch: base (ppi) = value × 1. Common use: Digital Image Resolution. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Pixel per centimeter (px/cm); si | Common units | Pixel per centimeter: base (ppi) = value × 2.54. Common use: Digital Image Resolution. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Pixel per millimeter (px/mm); si | Specialist units | Pixel per millimeter: base (ppi) = value × 25.4. Common use: Digital Image Resolution. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Dot per inch (dpi); si | Specialist units | Dot per inch: base (ppi) = value × 1. Common use: Digital Image Resolution. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Dot per centimeter (dpcm); si | Specialist units | Dot per centimeter: base (ppi) = value × 2.54. Common use: Digital Image Resolution. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
Sources: NIST: SP 811 Appendix B.8: conversion factors; BIPM: SI prefixes
Precision of digital image resolution conversions
All 5 digital image resolution units convert through Pixel per inch (ppi). 5 have an exact defined relationship to the base unit and 0 are conventional or measured values. Results and the tables on this page come from the same engine, so a table value can be checked against the converter directly.
Standard display shows up to six decimal places, switching to scientific notation for very large or small values. Calculation uses JavaScript binary floating point independently of display rounding, so extra digits are not a claim about measurement accuracy. Each unit lists its own source; a citation records where the definition comes from, not an independent review. See Conversion methodology for the review and correction process.