I have two copies of "The Associated Press Stylebook and Libel Manual," and
here is what it says regarding the use of metric units (from the 1998
edition). When you read this, you will see that most AP reporters are going
against the instructions given in the AP Stylebook! Here is the full
quotation:
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--METRIC SYSTEM-- In general, metric terms should be included in a story
when they are relevant.
There are no hard-and-fast rules on when they are relevant, but the
following two guidelines have been developed to cover questions likely to
arise as metric measurements gain increased acceptance in the United States:
-- Use metric terms when they are the *primary form*
[emphasis mine -- JJW] in which the source of a story has provided
statistics. Follow the metric units with equivalents in the terms more
widely known in the United States. Normally, the equivalent should be in
parentheses after the metric figure. A general statement such as: "A
kilometer equals about five-eighths of a mile," would be acceptable,
however, to avoid repeated use of parenthetical equivalents in a story that
uses kilometers many times.
-- Provide metric equivalents for traditional forms if a metric unit has
become widely known. As speedometers with kilometer markings become more
prevalent, for example, a story about speed limits might list miles per hour
and *provide kilometers per hour in parentheses* [emphasis mine -- JJW].
ABBREVIATIONS: The abbreviation "mm" for millimeter is acceptable in
references to film widths (8 mm film) and weapons (a 105 mm cannon). (Note
space between numeral and abbreviation.)
Do not otherwise use metric abbreviations in news copy.
The principal abbreviations, for reference in the event they are used by a
source, are: "g" (gram), "kg" (kilogram), "t" (metric ton), "m" (meter),
"cm" (centimeter), "km" (kilometer), "mm" (millimeter), "L" (liter, capital
"L" to avoid confusion with the figure "1") and "mL" (milliliter).
CONVERSION FORMULAS: A conversion table for frequently used metric terms
follows.
In addition, separate entries for "gram," "meter," "liter," "Celsius" and
other frequently used metric units define them and give examples of how to
convert them to equivalents in the terminology that has been used in the
United States. Similarly, entries for "pound," "inch," "quart,"
"Fahrenheit," etc., contain examples of how to convert these terms to metric
forms.
To avoid the need for long strings of figures, prefixes are added to the
metric units to denote fractional elements or large multiples. The prefixes
are: "pico-" (one-trillionth), "nano-" (one-billionth), "micro-"
(one-millionth), "milli-" (one-thousandth), "centi-" (one-hundredth),
"deci-" (one-tenth), "deka-" (10 units), "hecto-" (100 units), "giga-" (1
billion units), "tera-" (1 trillion units). Entries for each prefix show
how to convert a unit preceeded by the prefix to the basic unit.
<The conversion chart is just like ones we've all seen before, so I won't
reproduce it here.>
Jason
