UCUM can represent any number of valid units derived from 7 basic units. To that end, the standard combines various components:

• Basic units

metre (m, length)

second (s, time)

gram (g, mass)

radian (rad, angle)

Kelvin (K, temperature)

Coulomb (C, electric charge)

candela (cd, luminous intensity)

• derived units with conversion factors and formulas for the reduction to base units
• prefixes, i.e. a list of 30 standard prefixes to generate multiples (e.g. k for kilo, multiplier 10³) or fractions (e.g. d for deci, multiplier 10-1) of measurement units
• symbols and operators as well as syntax rules for their combination as follows:

<sign >	::=	“+” | “-”
<digit >	::=	“0” | “1” | “2” | “3” | “4” | “5” | “6” | “7” | “8” | “9”
<digits >	::=	<digit ><digits > | <digit >
<factor >	::=	<digits >
<exponent >	::=	<sign ><digits > | <digits >
<simple-unit >	::=	<ATOM-SYMBOL > | <PREFIX-SYMBOL ><ATOM-SYMBOL[metric] >
<annotatable >	::=	<simple-unit ><exponent > | <simple-unit >
<component >	::=	<annotatable ><annotation >| <annotatable >| <annotation >| <factor >| “(”<term >“)”
<term >	::=	<term >“.”<component > | <term >“/”<component > | <component >
<main-term >	::=	“/”<term > | <term >
<annotation >	::=	“{”<ANNOTATION-STRING >“}”