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Abbreviations of units

Units of length, weight, and many other quantities are abbreviations:

Unit name

Abbreviation

Unit name

Abbreviation

ampere

A

inch

in

degrees Celsius

C

joule

J

calorie

cal

kilogram

kg

carat

kt

litre

1 / L

cent

c

metre

m

centimetre

cm

miles per hour

mph

coulomb

C

milligram

mg

degrees Fahrenheit

F

minute

min

dozen

doz

ounce

oz

foot

ft

pound

lb

gallon

gal

yard

yd

hertz

Hz

year

yr

hour

h

You need to use a space between the number and the abbreviation. Also, there is no need to use a period after the abbreviation.

If you’re using the abbreviation as an adjective rather than as a direct measurement of the unit, then you need to put a hyphen between the number and the abbreviation. For instance, in this sentence, we’re using the abbreviation as an adjective:

Go get us a 20-kg bag of potatoes.

‘20-kg’ is an adjective describing the noun ‘bag’. So we need to put a hyphen between the ‘20’ and the abbreviation ‘kg’. However, there’s no need to use a hyphen when we’re using a linking verb and a subject complement:

Abbreviations of units