Inches to Millimetres Converter

Typography measures type in small length units, and the catch is that the word “point” means slightly different things in different traditions. The modern PostScript point — the one used by CSS, PDF and virtually all design software — is exactly 1/72 of an inch, about 0.3528 mm, and twelve of them make a pica. Screens add the CSS pixel, defined as 1/96 of an inch, so one point equals 1.333 pixels and the familiar 12 pt body text is 16 px. Older systems survive too: the TeX and American printer’s point is 1/72.27 inch, a hair smaller, while the European Didot point is larger at about 0.376 mm, with twelve Didots making a cicero. Word processors count in twips — twentieths of a point, so 1,440 to the inch — and newspapers still measure column depth in agates, fourteen to the inch. TeX even has its own microscopic units, the big point (identical to the PostScript point) and the scaled point, of which there are 65,536 in a single TeX point. One thing this converter deliberately leaves out is relative units like em, rem, ex and ch: those scale with the current font size, so they have no fixed length and can’t be converted without knowing that size. Everything here is stored as an exact number of millimetres, so any conversion is just your value turned into millimetres and back out into the unit you want.