In text use metric units, not imperial, unless the latter is the system used in the country being written about (eg the US and UK – note that US and UK imperial units often differ).
For measures of area above 1000 hectares, convert to sq km.
Spell out the following (and use numerals): acre, hectare, hour, gallon, knot, mile, millibar, minute, nautical mile, quart, pint, ton, tonne. (Exception: spell out numbers one to nine for measurements of time.)
6 hectares
7 miles
40 gallons
10 pints
two minutes
Use the following abbreviations and symbols for both singular and plural measurements.
Abbreviations should be repeated if they are closed up.
14km to 16km; but 14 to 16 sq km
Note: do not use the abbreviation unless a numeral precedes it. When high numbers appear with a unit of measure, abbreviations are retained.
7 billion kg; 2 million sq km
AM Amplitude Modulation (eg 1089AM)
cL centilitre [US: centiliter]
cm centimetre [US: centimeter]
cc cubic centimetre [US: centimeter]
° degree (latitude and longitude)
°C degree Celsius (but spell out degree in ‘360-degree view’ or ‘90-degree angle’)
°F degree Fahrenheit
FM Frequency Modulation (eg 106.5FM)
ft foot
g gram
HP horsepower
Hz hertz
in inches
kg kilogram
kHz kilohertz
km kilometre [US: kilometer]
km/h kilometres per hour [US: kilometers]
km/L kilometres per litre [US: kilometers]
L litre [US: liter]
lb pound
m metre [US: meter]
MHz megahertz
mph miles per hour
mg milligram
mL millilitre [US: milliliter]
mm millimetre [US: millimeter]
oz ounce
% percent
V volt
yd yard
cu metre cubic metre [US: meter]
sq cm square centimetre [US: centimeter]
sq in square inches
sq ft square feet
sq km square kilometre [US: kilometer]
sq metre square metre [US: meter]
sq miles square mile