To indicate the dimensions of objects most of the world uses the metric system. The US seem to remain stuck in their medieval system of feet, inches, yards and slightly odd paper sizes. Meanwhile designers stick to a completely different system of measurement called points. To confuse things even more, there a PostScript points, pica points and didot points. Weird….
When Adobe created PostScript, they added their own system of points. There are exactly 72 PostScript points in 1 inch.
- 1 PostScript point =0.35277138 mm = 1.00375001 pica point = 0.01388888 inch
The Didot system originated in France but was used in most of Europe.
- 1 didot point = 0.376065 mm = 1.07007 pica point = 0.0148057 inch
- 1 cicero equals 12 didot points.
This system was developed in England and used in Great-Britain and the US.
- 1 pica point = 0.35146 mm = 0.93457 didot point = 0.013837 inch
- 1 pica equals 12 pica points.
Inches, feet and yards
I don’t know if it is an urban myth but I once read one of the US space rockets exploded because of a mistake caused by a rounding error in a conversion routine between inches and millimeters.
- 1 inch = 25.4 mm
- 1 foot = 12 inch = 304.80 mm
- 1 yard = 3 feet = 914.4 mm
Other sources of information
Convert-Me is a nice site that offers conversion tools for almost everything.