# Hypertext Help with LaTeXLengths

A length is a measure of distance. Many LaTeX commands take a length as an argument. A length of one inch is specified by typing 1in or, to specify the same length using metric units, by typing 2.54cm.

## Units

LaTeX knows about the following common units.
• in - inches
• mm - millimeters
• cm - centimeters
• pt - points (about 1/72 inch)
• em - approximately the width of an "M" in the current font
• ex - approximately the height of an "x" in the current font
And the following less common units
• pc - pica (12pt/pc)
• bp - big pt (72bp/in)
• dd - didôt (1157dd=1238pt)
• cc - cîcero (12dd/cc)
• sp - scaled point (65536sp/pt)
Lengths may also be negative, for example, -1.5em.
Note that the number 0 by itself is not a length; it must be specified as 0in or 0pt, for example.

## Length commands

A length may also be specified by a length command. An example is \parindent whose value specifies the current width of the indentation which begins paragraphs. Multiples of such length commands may be specified, for example by writing 2.5\parindent or -0.1\parindent.

Some length commands are

• \parindent - normal paragraph indentation
• \baselineskip - normal vertical distance between lines in a paragraph
• \parskip - the extra vertical space between paragraphs
• \textwidth - the width of text on the page
• \linewidth - width of a line in the local environment
• \textheight - the height of text on the page
• \unitlength - units of lenght in Picture Environment
All length commands are robust and should not be preceded by a \protect command.

## Rubber lengths

Most lengths have a fixed value. However, LaTeX also allows for "rubber" lengths; these have a natural length plus a degree of elasticity. For example, the \fill length command has a natural length of zero but is infinitely stretchable, so that a space of width \fill will try to stretch as much as possible. Multiplying a rubber length by a fixed factor destroys its elasticity: 0.5\fill becomes a rigid length with a value of zero.

## Setting values for length commands

The following LaTeX commands define and manipulate the value of length commands