Grammar Guide

Express all specific measured quantities (dimensions, degrees, weights, distances, sums of money, etc.) in numeral form.

Correct Incorrect
1.3 seconds or 1.3 sec One point three seconds
$25,000 Twenty-five thousand dollars
2 amp two amperes


Write numbers beginning a sentence as words.

Correct Incorrect
Twenty-three screws are included. 23 screws are included.


Write approximate or non-specific numbers in a sentence as words.

Correct Incorrect
about half; a quarter of; four times as often. about ½; a ¼ of; 4 times as often.
'60s, '70s & '80s or 1960s, 1970s or 1980s 60s, 70s, & 80s or Sixties, Seventies, and Eighties


Hyphenate all compound numbers from twenty-one through ninety-nine in a sentence.

Correct Incorrect
There are twenty-three screws included. There are twenty three screws included.


Write decimals as numbers. Place a zero in front of decimals with no whole number.

Correct Incorrect
0.128 mm .128 mm
1.33 mm One point three millimeters


Don't use a space between whole numbers and fractions. Use fractions on the web.

Print Correct Incorrect
2⅔ 2-2/3
Web Correct Incorrect
2-3/4 2 3/4
1-1/2" 1.5"


Use a space between numbers and units of measure.

Correct Incorrect
89 mm Piston & Liner Set 89mm Piston & Liner Set


Do not use a space between numbers and measurement signs.

Correct Incorrect
11% 11 %
A 36° angle. A 36 ° angle.
5' 3" 5 ' 3 "


Use decimals with temperature scales. Do not express temperature degrees with the ° symbol. Use a space after the number.

Correct Incorrect
15.1 F 15.1F
-45 C -45°C
2,700 K .045 °K


For imperial measurements, use fractions for print, and decimals for web.

Print Correct Print Incorrect
516 0.3125"
Painted, 60 spoke, 15" x 4 ½" Painted, 60 spoke, 15"x4.5"
Web Correct Web Incorrect
Painted, 60 spoke, 15" x 4.5" Painted, 60 spoke, 15" x 4 ½"


Use decimals with metric.

Correct Incorrect
7.9375 mm 0.3125"


Units of measure are case-sensitive. mm is millimeter (one thousandth of a meter) Mm is megameter (1,000,000 meters)

Correct Incorrect
A 5 mm x 0.8 mm pitch tap A 5 MM x 0.8 mm pitch tap."


Treat unit names like ordinary nouns when spelled out in full. Thus the names of units start with a lower-case letter, except at the beginning of a sentence or in a title. When repeating multiple measurements consider spelling out the unit name for the first instance then using the abbreviation on following instances.

Unit Name Unit of Measure Use
millimeter mm 1 mm
centimeter cm 6 cm
amperes/amps amp or A 4 A
volts V 8 V
watts W 12 W
joules J 6.7 J
lumens lm 142 lm
ohms ohms 10 Ω
decibels dB 120 dB
hertz Hz 160 Hz
inches " or in 6 in
feet ' or ft 14 ft
pound lb 10 lb
ounce oz 10 oz
AM/PM am/pm 8 am
pressure (pounds per square inch) psi 35 psi
torque (foot-pounds) ft-lb 80 ft-lb
torque (inch-pounds) in-lb 120 in-lb


Do not use "plural" units of measure.

Correct Incorrect
2 mL 2 mLs
14 lb 14 lbs


Do not use a period after a unit of measure. They are not abbreviations.

Correct Incorrect
14 lb 14 lb.
12' 9" 12 ft. 9 in.


Express dimensions by length, width, and height/depth, separated by an "x" with spaces in between. List dimension units when needed for clarification.

Correct Incorrect
48" x 12" x 2" 48"x12"x2"
8.5 cm x 11 mm x 1 cm 8.5cmx11mmx1cm
Size: 7½"(l) x 7⅘"(w) x 2¾"(h) with 3" end stop Size: 71/2" (L)x74/5" (W)x23/4" (H) with 3" end stop


Do not mix imperial and metric.

Correct Incorrect
21.59 cm x 1 mm 8 ½" x 1 mm


Do not mix symbols and units.

Correct Incorrect
1" x 6' Easy Loom 1" x 6 ft Easy Loom
1 in x 6 ft Easy Loom 1" x 6 ft Easy Loom


For a range of numbers, use an n-dash with no spaces before or after. For dates, use the full year for the first date and the 2 digit abbreviation for the second.

Correct Incorrect
Dia: 15"–16"; Grip: 2 3/4"–3 1/8" Dia: 15" - 16"; Grip: 2 3/4" – 3 1/8"
1968-73 1968 - 73


Add a space after w/
Change "O" ring to O-ring
' (single prime)
" (double prime)
‘’ (single quotation marks)
“” (double quotation marks)
’ (apostrophe)
° Bullets - bullets are thoughts and don't have periods at the end. Bullets are a single sentence. They are more than 1 sentence make 2 bullets or rewrite.