Type measurement
Although most software allows a user to access measurements such as centimetres, inches and millimetres,
typesetting uses its own measurement system.
For three hundred years after Gutenburg, no standard system of measurement existed. Type foundries (places where type
was designed and cast from metal) used their own systems.
This meant that type from one house often could not be used successfully by other foundries or printers. Sometimes,
the name given to a size of type from one foundry was the same name given to a different type size from another foundry.
The first attempt at a standard system of measurement was devised in 1737 by a French type designer called Pierre Simon
Fournier. He divided one premetric French foot into 144 equal parts and called these parts points. One of Fournier's
points was equivalent to 0.0137 of an English inch.
After Fournier's death, another type designer, Francois Ambrose Didot advocated Fournier's systems should be based on
the legal foot measure of France.
The Didot point equals 0.0148 of an English inch and the cicero Ð Didot's equivalent to the pica Ð measures 0.1776 of
an inch. The Didot system is still used on continental Europe.
Other attempts by English-speaking designers followed the French example, but no consensus of opinion was reached until
the late 19th century. In 1871, the great fire of Chicago destroyed the premises of Marder, Luse and Co., one of America's
leading type foundries. As a result, a new system was devised to replace the lost matrixes. It was decided to use the
pica as the main measurement system. This pica was divided into 12 parts called points. In 1898, British type founders
adopted the American measurement and the system became the international standard for English-speaking countries.
Picas and points
A pica is equivalent to 0.166044 of an inch, and is divided into 12 points. Although not mathematically precise, 72
points sizes are specified as being equivalent to one inch, and 36 points sizes are half an inch.
Points are used to measure all manner of typographical elements, including the thickness of spaces, the height of type,
leading, and the size of rules and borders.
A type face can have different apparent sizes but still be set as the same point size.
Type that is bigger than the point size is called "big on the body; smaller type is called "small on the body".
Agates
Agate is a measurement used by advertisers and newspapers to measure the size of columns of type.
One agate is approximately 5.5 points in size; there are 14 agate lines to one inch.
Ems and ens
Another measuring device used by typographers and printers is called the em. While pica is a linear measurement, used
to specify the height, width and depth, an em is used to determine the area of a square of an area.
It is equal to the square of the type size used. For example, 36 point type measured in ems would be equal to a 362
or .5 inch on all sides. Another measure of area is called "en". The en is half the size of an em and so type set in
36 points would have an en of 36 by 18 points.
Both em and en are used to specify the indents of lines of text. If the copy is to set in 12 points, the em indent will
also be 12 points, and the en indent will be 6 points.
Written by Geoffrey Fletcher
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