Numbers and Symbols

Dates

The IEEE Policies and Procedures (Jan. 2000) specify the following formats for dates:
E-mail and formal correspondence: day, month, year—for example, 6 January 2004.
Software applications: four-digit year, two-digit month, two-digit day—for example, 2004-01-06.

Centuries: Use the symbol for ordinal numbers—for example, 20th century. Note: CMS spells out the century—for example, twentieth century.

Decades: The abbreviation is ’90s, not ‘90s. Transactions use the four-digit format: 1990s.

Numerals

Spell out integers one through nine and use numerals for 10 on, except in the following cases:

As a general rule, numerals should be used even for one through nine when the integer is coupled with a symbol or unit of measurement (2°, 3 V). By the same token, numerals should be used with percentages even for one through nine (a 5 percent drop; 3 percent responded; 3 to 6 percent). However, in nontechnical passages, numbers less than 10 used with common units, especially time units, may look better spelled out, as do numbers used with approximate measurements:

 

the program ran in 8 minutes [exact measurement]

but

a report from eight years ago said [nontechnical]

 

he lives eight miles down the road [nontechnical]

 

about eight or nine centimeters [approximate]

Spell out a number at the beginning of a sentence or recast the sentence.

In general, for units of measure, spell out on first use and abbreviate thereafter.

When a sentence includes both an integer less than nine and an integer greater than nine to describe something in the same category, use numerals for consistency—for example, The network can have 4, 8, or 16 nodes.

A compound adjective consisting of a number and an abbreviation is hyphenated. For example, 24-Kbyte memory.

Numbers with four digits or more have commas: 1,000, 10,000. Exceptions include page numbers and dates (CMS 9.55). Precede decimal fractions with values of less than one with a zero to prevent the reader from overlooking the period: 0.1 (however, observe the exceptions listed in CMS 3.70 and 9.19). And remember, they’re singular: 0.1 inch, not 0.1 inches.

Use an s to create plurals of numerals:

  • the early 1920s
  • in twos, threes, and zeros
  • he had a collection of 386s and 486s

Fonts and computers are inconsistent in the treatment and availability of fraction symbols. For in-text fractions, therefore, full-size numerals with a slash are usually preferred: 1/2, not ½. In more complicated mathematical expressions set in MathType, built-up fractions are generally used: numerator over denominator, separated by a horizontal line. In mixed numerals, put a hyphen between the integer and the fraction:

  • 8-1/2 inches wide
  • 24-5/8-mile track

For further reference see CMS Chapter 9, especially the parts on scientific and technical usage.

Symbols and signs

Use symbols in text only when you are certain that readers are familiar with them.

Multiplication symbol: Use the multiplication sign “×” instead of “by” when numerals refer to dimensions: 3 × 5 cm box; 3 in. × 5 ft. board.

Spacing of characters for units of measurement and symbols: Abbreviations for units of measurement, even if one letter, are separated from the numeral by a space (3 V, 5 m, 14 mm). Actual symbols, as opposed to abbreviations for units, can be closed up, for example, 42°30' for 42 degrees, 30 minutes latitude.

Use sq. ft., not “ft2.”

Do not use abbreviations when the reference is indefinite or casual—say “several gigahertz” not “several GHz.” However, where brevity is a key factor—for example, in new product write-ups and tables—use symbols liberally.

When defining variables in run-in text, use “is” rather than “=”; for example, “where t is the temperature,” not “where t = the temperature.”

Use the word “percent” in text; use the % symbol only in figures and tables.

Telephone and fax numbers

The IEEE Policies and Procedures specify the following format for phone and fax numbers:

In North America: +1 area code xxx xxxx; for example, +1 714 821 8380

Outside North America: +country code city code xxx xxxx; for example, in Belgium, +32 3 770 2242

 

WEIGHTS AND MEASURES*

Unit

Abbreviation or symbol

Other equivalents

Metric equivalent

WEIGHT

Avoirdupois (US standard)

ton

     

short ton

 

2,000 pounds, 20 short hundredweight,

0.907 metric ton

long ton

 

2,240 pounds, 20 long hundredweight,

1.016 metric ton

hundredweight

cwt

   

short hundredweight

 

100 pounds,

0.05 short ton

45.359 kilograms

long hundredweight

 

112 pounds,

0.05 long ton

50.802 kilograms

pound

lb or lb avdp also #

16 ounces, 7,000 grains

0.454 kilogram

ounce

oz or oz avdp

16 drams, 437.5 grains, 0.0625 pound

28.350 grams

dram

dr or dr avdp

27.344 grains,

0.0625 ounce

1.772 grams

grain

gr

0.037 dram,

0.002286 ounce

0.0648 gram

Troy

pound

lb

12 ounces,

240 pennyweight,

5,760 grains

0.373 kilogram

ounce

oz

20 pennyweight,

480 grains, 0.083 pound

31.103 grams

pennyweight

dwt also pwt

24 grains, 0.05 ounce

1.555 grams

grain

gr

0.042 pennyweight, 0.002083 ounce

0.0648 gram

Apothecaries

pound

lb ap

12 ounces, 5,760 grains

0.373 kilogram

ounce

oz ap

8 drams, 480 grains, 0.083 pound

31.103 grams

dram

dr ap

3 scruples, 60 grains

3.888 grams

scruple

s ap

20 grains, 0.333 dram

1.296 grams

         

grain

gr

0.05 scruple,

0.002083 ounce,

0.0166 dram

0.0648 gram

CAPACITY

US liquid measure

gallon

gal

4 quarts

(231 cubic inches)

3.785 liters

quart

qt

2 pints

(57.75 cubic inches)

0.946 liter

pint

pt

4 gills

(28.875 cubic inches)

473.176 milliliters

gill

gi

4 fluid ounces

(7.219 cubic inches)

118.294 milliliters

fluid ounce

fl oz

8 fluid drams (1.805 cubic inches)

29.573 milliliters

fluid dram

fl dr

60 minims

(0.226 cubic inch)

3.697 milliliters

minim

min

1/60 fluid dram (0.003760 cubic inch)

0.061610 milliliter

US dry measure

bushel

bu

4 pecks

(2150.42 cubic inches)

35.239 liters

peck

pk

8 quarts

(537.605 cubic inches)

8.810 liters

quart

qt

2 pints

(67.201 cubic inches)

1.101 liters

pint

pt

½ quart (33.600 cubic inches)

0.551 liter

British imperial liquid and dry measure

bushel

bu

4 pecks

(2,219.36 cubic inches)

36.369 liters

peck

pk

2 gallons

(554.84 cubic inches)

9.092 liters

gallon

gal

4 quarts

(277.420 cubic inches)

4.546 liters

quart

qt

2 pints

(69.355 cubic inches)

1.136 liters

pint

pt

4 gills

(34.678 cubic inches)

568.26 milliliters

gill

gi

5 fluid ounces

(8.669 cubic inches)

142.066 milliliters

fluid ounce

fl oz

8 fluid drams

(1.7339 cubic inches)

28.412 milliliters

fluid dram

fl dr

60 minims

(0.216734 cubic inch)

3.5516 milliliters

minim

min

1/60 fluid dram (0.003612 cubic inch)

0.059194 milliliter

LENGTH

mile

mi

5,280 feet, 1,760 yards, 320 rods

1.609 kilometers

rod

rd

5.50 yards, 16.5 feet

5.029 meters

yard

yd

3 feet, 36 inches

0.9144 meter

foot

ft or '

12 inches, 0.333 yard

30.48 centimeters

inch

in or "

0.083 foot, 0.028 yard

2.54 centimeters

AREA

acre

 

4,840 square yards, 43,560 square feet

0.405 hectare,

4,047 square meters

square inch

sq in or in2

0.0069 square foot, 0.00077 square yard

6.452 square centimeters

square foot

sq ft or ft2

144 square inches,

0.111 square yard

0.093 square meter

square yard

sq yd or yd2

1,296 square inches,

9 square feet

0.836 square meter

square rod

sq rd or rd2

30.25 square yards, 0.00625 acre

25.293 square meters

square mile

sq mi or mi2

640 acres,

102,400 square rods

2.590 square kilometers


VOLUME

cubic yard

cu yd or yd3

27 cubic feet,

46,656 cubic inches

0.765 cubic meter

cubic foot

cu ft or ft3

1,728 cubic inches, 0.0370 cubic yard

0.028 cubic meter

cubic inch

cu in or in3

0.00058 cubic foot, 0.000021 cubic yard

16.387 cubic centimeters

*Adapted from Merriam-Webster’s Collegiate Dictionary, 11th ed., 2003.

         

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