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International units and numerical values (was Re: Thousands separator for the Euro?)

From: Christophe Pouylau <christophe.pouylau@wanadoo.fr>
Date: Wed, 09 Aug 2000 09:16:57 +0900
Message-Id: <>
To: www-international@w3.org
Following up on this interesting question, I would like to clarify some
typographical French conventions, and international guidelines for numerical
values and units.

1. Using a dot as a thousand separator is pretty informal in France. The
legal rule dictates that thousands must be separated by one fourth of a
quadratin, also called 'fine space' (Vivin, 1975; Bulcourt et al, 1984;
Perrousseaux, 1996); a quadratin being "a square space with a side length
equal to the font size used". In a 12 pt font size, thousands should be
separated by 3 pt or 3 * 0.3759 mm = 1.13 mm. Major operating systems
(Microsoft, Apple, Sun, ...) guidelines follow this rule: When a fourth of
quadratin is not available in the font used, it's better to use a normal
(non-breaking) space than no space at all, or a dot, in this case. In fact,
this very rule applies to spaces preceding all 'double' punctuation signs
(semicolon, question mark, exclamation mark) except the colon (:) which
should follow a regular non-breaking space (quadratin). French speaking
readers, please note that, in typography, 'espace' is of feminine gender:
une espace fine.

2. When abbreviated, most frequent unit multipliers (k for kilo-, h for
hecto-, da for deca-) and all dividers (d for deci-, c for centi-, m for
milli-, ...) should be written in lowercase, whether Latin or Greek (mu sign
for micro, ...). However, mega-, giga-, and tera- should be abbreviated with
an uppercase letter (respectively M, G and T). Please note that this rule
not only applies to France, but to all countries that have adopted the
International System of measurement and units (SI).

3. Units should follow numerical values, and be separated from them by a
non-breaking space (quadratin).

4. When part of sentence, units should only be abbreviated when following a
decimal (non-integer) value or a fraction (Bulcourt et al, 1984).
e.g.: Cette voiture est vendue 24 950 euros (all lowercase).
Elle gagne 3 257,56 竄ャ exactement (using the currency symbol).
Prix : 3 600 竄ャ (acceptable use of the currency symbol, since not part of a

For more information on local numerical formats, a good start point is the
excellent book by Nadine Kano 'Developing International Software for Windows
95 and Windows NT', presently out of print by available online:

Usage guidelines for the International System of Units can be found on the
National (US) Institute of Standards and Technology Web site:
Particularly interesting guidelines for binary multiples (bits and bytes):

Thanks for your patience reading this long post.

C. Pouylau
L10N consultant
Received on Thursday, 10 August 2000 20:17:35 UTC

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