Typographic units
Free tools from the Typographic units group.

cm to ptConvert centimetres to points, the unit Word and layout programs use for font size.
em to pxConvert CSS em units to pixels and vice versa. Adjustable parent font size.
em to remConvert CSS em to rem with any parent font-size and any root font-size.
in to ptConvert inches to points for page sizes, margins and bleed. The selector gives PostScript, TeX and Didot points.
mm to ptConvert millimeters to points to set a stroke weight, a font size or a page size.
pc to pxConvert picas to pixels at any DPI. The selector covers all three pica systems.
pt to cmConvert points to centimetres and see how big a font size prints. The selector also covers TeX and Didot points.
pt to inConvert points to inches and see how tall a font size really prints. The selector also covers TeX and Didot points.
pt to mmConvert points to millimeters and see how tall letters and how thick lines come out in print.
pt to pxConvert typographic points to pixels and vice versa. For designers and developers.
px to emConvert pixels to CSS em at any parent font size.
px to pcConvert pixels to picas at any DPI. The result can also be written as 20p3.
px to ptConvert pixels to typographic points. For print, PDF page sizes and email signatures.
px to remConvert pixels to CSS rem at any base font size.
rem to emConvert CSS rem to em with any root font-size and any parent font-size.
rem to pxConvert CSS rem units to pixels at any base font size.