(number of significant decimal digits)
Metric System
Didot System
PostScript (current DTP)
Imperial Units
Pica System
pica [pc,pi]
Abc
Type Sizes Table (Didot System)
2p Nonplusultra 2.5p Microscopique 3p Brilliant 4p Diamond 5p Pearl 6p Nonparel 7p Minion (mignon) 8p Petit 9p Bourgeois 10p Garmond 11p Brevier 12p Cicero (pica) 14p Mittel (English) 16p Tertia 20p Double Garmond (Paragon) 24p Double Pica 28p Double English (2 Mittel) 32p Double Tertia 36p Double Paragon 48p Canon
Typographic Units Systems
Didot System - used in Europe except UK
1 point = 1p = 1/2660 m = 0.37594 mm
1 cicero (pica) = 1cc = 12 p = 12/2660 m = 4.511278 mm

Pica System - UK and USA
1 point = 1pt = 350/996 mm = 0.3514 mm
1 pica = 1pc = 12 pt = 4.216867 mm

PostScript - current DTP point system used e.g in CSS (Cascading Style Sheets).
1 point = 1pt = 1/72in (cala) = 0.3528 mm
1 pica = 1pc = 12pt= 1/6in (cala) = 4.233(3) mm

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