Pica

Formal Definition

The pica (symbol: pc) is a typographic unit of measurement equal to 12 points. In the modern PostScript/DTP standard, where one point equals exactly 1/72 of an inch, one pica equals exactly 1/6 of an inch (approximately 4.233 mm). There are exactly 6 picas in one inch. The pica serves as the primary unit for larger typographic measurements — column widths, page margins, gutters, and other structural elements of page layout.

The pica occupies a middle ground in the typographic measurement system: it is large enough to conveniently express page-level dimensions (a standard US letter page is 51 picas wide by 66 picas tall) but small enough to provide useful precision for column widths and margins. In professional page layout, measurements are often expressed in picas and points together — for example, "22p6" means 22 picas and 6 points (22.5 picas total).

Relationship to Other Units

One pica equals 12 points, 16 pixels (at 96 DPI), approximately 4.233 millimeters, or approximately 0.1667 inches. In CSS, the pica is a recognized unit (pc), though it is rarely used in web design compared to pixels, ems, or rems. The pica-and-points system (e.g., "22p6") is the traditional way of expressing typographic measurements in professional publishing software such as Adobe InDesign and QuarkXPress.

Origin of the Name

The origin of the word "pica" in typography is debated. The most widely accepted theory traces it to the Medieval Latin "pica," referring to a book of ecclesiastical rules for determining church services (the "Pie" or "Pica"). This book was printed in a type size that became known as "pica" — approximately 12 points. Another theory connects it to the Latin "pica" (magpie), perhaps because the random appearance of black-and-white type on a page resembled a magpie's plumage, or because the book of rules resembled a "pie" of mixed type.

Historical Usage

Before the point system, "pica" was one of the named type sizes used in English-language printing, corresponding to approximately 12 points (about 1/6 inch). The name dates back to at least the 15th century in English printing. When the American point system was standardized in 1886, the pica was formalized as exactly 12 points, and it evolved from a type size name into a unit of measurement used for page layout dimensions.

Early Printing

The pica as a named type size existed in English printing from at least the late 15th century. In the early days of movable type, type sizes were identified by name rather than number, and "pica" referred to type of a specific size — roughly equivalent to modern 12-point type. The pica body was a convenient reference size for English printers: it was large enough to be easily readable and small enough to be economical, making it the standard body text size for many applications.

Standardization as a Measurement

When the American point system was formalized in 1886, the pica was standardized as 12 points. This gave the pica a precise numerical value (12 × 0.01383 inches = 0.16604 inches, or approximately 1/6 inch). The pica became the standard unit for measuring column widths, page margins, and other layout dimensions in American and British printing. Printers used pica rulers (also called line gauges or typometers) marked in picas and points.

Desktop Publishing

The transition to desktop publishing in the 1980s preserved the pica as a fundamental unit. Adobe's PostScript language defined the pica as exactly 12 PostScript points (12/72 inch = 1/6 inch exactly). PageMaker (1985), QuarkXPress (1987), and later InDesign (1999) all used picas as a primary measurement unit, with measurement fields accepting values in the "picas and points" format (e.g., 22p6). This convention continues in modern design software.

Declining Everyday Use

While picas remain the standard in professional book and magazine design, their use has declined in web design and general office work. Web designers prefer pixels, ems, and percentages. Word processors default to inches or centimeters for page layout. However, in the specialized world of print design, the pica remains indispensable — a professional typographer or book designer would no more abandon picas than a carpenter would abandon inches.

In Professional Page Layout

Picas are the primary unit of measurement in professional page layout software. Adobe InDesign, the industry-standard tool for book, magazine, and newspaper design, defaults to picas for most measurements. Designers specify column widths, gutters, margins, and baseline grids in picas. A typical book page might have margins of 4p6 (4 picas, 6 points) and column widths of 22 picas. Magazine layouts commonly use column widths of 10 to 15 picas.

In Newspaper Design

Newspaper design traditionally uses picas extensively. Column widths are specified in picas, and the modular layout grids used for newspaper pages are built on pica-based measurements. A standard newspaper column width ranges from 10 to 14 picas depending on the paper's format and design. Photo widths, headline sizes, and spacing are all expressed in picas and points.

In Book Design

Book designers work primarily in picas. The type area of a book page — the rectangle containing the main text — is dimensioned in picas. Line length (measure) is expressed in picas, with optimal line lengths for readability typically falling between 45 and 75 characters, which translates to roughly 18 to 32 picas depending on the typeface and size. Margins, running headers, folios, and footnote areas are all measured in picas.

In Design Software

Anyone working with professional design software encounters picas. Adobe InDesign's default measurement system uses picas, and new users must learn to read pica-and-point notation (22p6 = 22 picas, 6 points = 22.5 picas). The Control panel, Measurements palette, and New Document dialog all display dimensions in picas unless the user changes the preference to inches or millimeters.

In Typography Education

Typography courses and textbooks teach the pica as a fundamental unit. Design students learn to think in picas when creating layouts, just as architects think in feet and inches. The ability to quickly convert between picas, points, and inches is a basic skill for graphic designers. Common reference points: a US letter page is 51 × 66 picas; an A4 page is approximately 49.7 × 70.3 picas.

In Print Specifications

When submitting files for professional printing, specifications often use picas. Trim sizes, bleed areas, gutter widths, and binding margins may be communicated in picas and points. Print production professionals, prepress technicians, and typesetters share a common vocabulary built on pica measurements.

In Typography Research

Typography research frequently reports measurements in picas. Studies of optimal line length for readability measure column widths in picas, as this is the natural unit for expressing typographic dimensions. Research findings such as "optimal line length is 21 to 24 picas for 10-point text" are directly applicable to design practice.

In Human Factors and Ergonomics

Human factors research on document readability uses picas when specifying layout parameters. Studies examining the effects of column width, margin size, and gutter width on reading speed and comprehension report these dimensions in picas. This allows findings to be directly applied in design guidelines.

In Library and Information Science

Library science and information design use picas for specifying the physical dimensions of printed catalog cards, labels, and information displays. The traditional library catalog card measured exactly 7.5 × 12.5 cm (approximately 17.7 × 29.6 picas), and its typographic specifications were expressed in picas and points.