ScanCalc

ScanCalc is a small JavaScript utility to convert between centimeters (cm), pixels and dots/inch (dpi).

Scan Calc
 cm  pixels  dpi
 pixels  dpi  cm
 dpi  cm  pixels

The JavaScript and HTML code that is ScanCalc is public domain, use it as you wish. Either save this page, or use the view source function to copy and paste the code to your own page.