Re: "em" should be horizontal, "ex" vertical

Clive Bruton (
Mon, 11 Aug 97 11:12:49 +0100

Date: Mon, 11 Aug 97 11:12:49 +0100
From: Clive Bruton <>
To: "Peter Flynn" <>, <>
Message-ID: <>
Subject: Re: "em" should be horizontal, "ex" vertical

Peter Flynn wrote at 11/8/97 10:59 am

>> While that's a good definition, typesetting practice /never/ uses "em"
>> as vertical measurement; an em is a horizontal measurement only, and an
>> "ex" is the vertical measurement.  This makes measurements based on
>> fonts size work with compressed an/or fat fonts.
>This is incorrect: pica ems are used for page depth and line spacing
>almost universally in the Anglo-American world. When did you last see
>a comp's spec specify print-area height in "ex"s?

Correct, the definition of an "em" is a *square* of any given body size, 
ie 9pt*9pt, 24pt*24pt, 72pt*72pt are all ems. The correct term for a 12pt 
em is a *pica* em as pointed out, an em is a relative unit.

-- Clive