Point (typography) - Traditional American Point System

Traditional American Point System

By the (Kasson) Metric Act of 1866 (Public Law 39-183), the US (survey) foot is 1200⁄₃₉₃₇ m. This is 0.0002% more than 304.8 mm, which is the length of the 1959 foot, used below. A typographic foot contains 72 picas or 864 points.

• Nelson C. Hawks, in 1879, used a printer’s foot of a statute foot decreased by 0.375%. Therefore, the traditional ratio 7200⁄₇₂₂₇ (which reduces to 800⁄₈₀₃) places Hawks’ point at 0.013 837 inch, or about 0.35146 mm.
• A second definition was proposed whereby there were exactly 996 printer’s points (= 83 picas) in 350 mm, which made the printer’s point about 0.013 848 867 inch ≈ 0.351405622 mm.
• Finally, Lawrence Johnson stated in a third definition of printer’s foot that it should be 249⁄₂₅₀ (99.6%) English foot. This means that the Johnson’s typographical point was 0.01383 inch, and was then converted by the 1959 value to 0.35136 mm.

In 1886, the Fifteenth Meeting of the Type Founders Association of the United States approved the so-called Johnson pica be adopted as the official standard. This makes the traditional American printer’s foot measure 11.952 inches (303.6 mm), or 303.5808 mm exactly, giving a point size of approximately 1⁄_72.27 of an inch, or 0.3515 mm.

This is the size of the point in the TeX computer typesetting system by Donald Knuth, which predates PostScript slightly. Thus the latter unit is sometimes called the TeX point.

Like the French Didot point, the traditional American printer’s point was replaced in the 1980s by the current computer-based DTP point system.