UCUM Symbols (Normative) – OPC Unified Architecture

Annex B UCUM Symbols (Normative)

B.1 Introduction - License

This Annex provides an excerpt from the UCUM Specification available at https://ucum.org.

The UCUM license is available in https://ucum.org/license. This license includes a disclaimer of warranties.

B.2 Representation

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>“}”

B.3 Tables of terminal symbols

B.3.1 General

The following tables define prefixes and unit symbols. The columns define:

The UCUM representation (Symbol (c/s))
The full name (Display Name)
The Print Symbol – recommended for display and printing
Value (for prefixes) is the scalar value by which the unit atom is multiplied if combined with the prefix.
Kind of Quantity (for units) is the quantity name.

Full name and print symbol are defined by other bodies and are out of scope of The Unified Code for Units of Measure.

B.3.2 Prefixes

The prefix symbols
Symbol (c/s)	Display Name	Print Symbol	value
Y	yotta	Y	1 × 1024
Z	zetta	Z	1 × 1021
E	exa	E	1 × 1018
P	peta	P	1 × 1015
T	tera	T	1 × 1012
G	giga	G	1 × 109
M	mega	M	1 × 106
k	kilo	k	1 × 103
h	hecto	h	1 × 102
da	deka	da	1 × 101
d	deci	d	1 × 10-1
c	centi	c	1 × 10-2
m	milli	m	1 × 10-3
u	micro	μ	1 × 10-6
n	nano	n	1 × 10-9
p	pico	p	1 × 10-12
f	femto	f	1 × 10-15
a	atto	a	1 × 10-18
z	zepto	z	1 × 10-21
y	yocto	y	1 × 10-24

Symbol (c/s)	Display Name	Print Symbol	value
The special prefix symbols for powers of 2 NOTE These symbols are for use in information technology as proposed by the IEEE.
Ki	kibi	Ki	1 × 10241
Mi	mebi	Mi	1 × 10242
Gi	gibi	Gi	1 × 10243
Ti	tebi	Ti	1 × 10244
Pi	pebi	Pi	1 × 10245
Ei	exbi	Ei	1 × 10246
Zi	zebi	Zi	1 × 10247
Yi	yobi	Yi	1 × 10248

B.3.3 Base units

The base units are used to define all the unit atoms of The Unified Code for Units of Measure according to its grammar and semantics.

The selection of the base and the order of the units in the base are not normative. Any other base is acceptable as long as there is an isomorphism between the group of units generated by the other base system and this one. All base units are metric.

Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
m	meter	m	length	yes
s	second	s	time	yes
g	gram	g	mass	yes
rad	radian	rad	plane angle	yes
K	kelvin	K	temperature	yes
C	coulomb	C	electric charge	yes
cd	candela	cd	luminous intensity	yes

B.3.4 Derived unit atoms

Dimensionless units NOTE The units ppb and ppt are deprecated because the names "billion" and "trillion" are ambiguous.
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
10*	the number ten for arbitrary powers	10n		no
10^	the number ten for arbitrary powers	10n		no
[pi]	the number pi	π		no
%	percent	%		no
[ppth]	parts per thousand	ppth		no
[ppm]	parts per million	ppm		no
[ppb]	parts per billion	ppb		no
[pptr]	parts per trillion	pptr		no

SI units NOTE Defined by CGPM (General Conference on Weights and Measures).
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
mol	mole	mol	amount of substance	yes
sr	steradian	sr	solid angle	yes
Hz	hertz	Hz	frequency	yes
N	newton	N	force	yes
Pa	pascal	Pa	pressure	yes
J	joule	J	energy	yes
W	watt	W	power	yes
A	ampère	A	electric current	yes
V	volt	V	electric potential	yes
F	farad	F	electric capacitance	yes
Ohm	ohm	Ω	electric resistance	yes
S	siemens	S	electric conductance	yes
Wb	weber	Wb	magnetic flux	yes
Cel	degree Celsius	°C	temperature	yes
T	tesla	T	magnetic flux density	yes
H	henry	H	inductance	yes
lm	lumen	lm	luminous flux	yes
lx	lux	lx	illuminance	yes
Bq	becquerel	Bq	radioactivity	yes
Gy	gray	Gy	energy dose	yes
Sv	sievert	Sv	dose equivalent	yes

Other units from ISO 1000, ISO 2955, and some from ANSI X3.50.
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
gon	gon, grade	□g	plane angle	no
deg	degree	°	plane angle	no
'	minute	'	plane angle	no
''	second	''	plane angle	no
l	liter	l	volume	yes
L	liter	L	volume	yes
ar	are	a	area	yes
min	minute	min	time	no
h	hour	h	time	no
d	day	d	time	no
a_t	tropical year	at	time	no
a_j	mean Julian year	aj	time	no
a_g	mean Gregorian year	ag	time	no
a	year	a	time	no
wk	week	wk	time	no
mo_s	synodal month	mos	time	no
mo_j	mean Julian month	moj	time	no
mo_g	mean Gregorian month	mog	time	no
mo	month	mo	time	no
t	tonne	t	mass	yes
bar	bar	bar	pressure	yes
u	unified atomic mass unit	u	mass	yes
eV	electronvolt	eV	energy	yes
AU	astronomic unit	AU	length	no
pc	parsec	pc	length	yes

Natural unit NOTE Fundamental constants of nature and units derived from these constants.
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[c]	velocity of light	c	velocity	yes
[h]	Planck constant	h	action	yes
[k]	Boltzmann constant	k	(unclassified)	yes
[eps_0]	permittivity of vacuum	ε0	electric permittivity	yes
[mu_0]	permeability of vacuum	μ0	magnetic permeability	yes
[e]	elementary charge	e	electric charge	yes
[m_e]	electron mass	me	mass	yes
[m_p]	proton mass	mp	mass	yes
[G]	Newtonian constant of gravitation	G	(unclassified)	yes
[g]	standard acceleration of free fall	gn	acceleration	yes
atm	standard atmosphere	atm	pressure	no
[ly]	light-year	l.y.	length	yes
gf	gram-force	gf	force	yes
[lbf_av]	pound force	lbf	force	no

CGS units NOTE The units of the older Centimeter-Gram-Second (CGS) system.
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
Ky	Kayser	K	lineic number	yes
Gal	Gal	Gal	acceleration	yes
dyn	dyne	dyn	force	yes
erg	erg	erg	energy	yes
P	Poise	P	dynamic viscosity	yes
Bi	Biot	Bi	electric current	yes
St	Stokes	St	kinematic viscosity	yes
Mx	Maxwell	Mx	flux of magnetic induction	yes
G	Gauss	Gs, G	magnetic flux density	yes
Oe	Oersted	Oe	magnetic field intensity	yes
Gb	Gilbert	Gb	magnetic tension	yes
sb	stilb	sb	lum. intensity density	yes
Lmb	Lambert	L	brightness	yes
ph	phot	ph	illuminance	yes
Ci	Curie	Ci	radioactivity	yes
R	Roentgen	R	ion dose	yes
RAD	radiation absorbed dose	RAD	energy dose	yes
REM	radiation equivalent man	REM	dose equivalent	yes

B.3.5 Customary unit atoms

International customary units NOTE The unified U.S. and British Imperial customary units, so called "international" customary units
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[in_i]	inch	in	length	no
[ft_i]	foot	ft	length	no
[yd_i]	yard	yd	length	no
[mi_i]	mile	mile	length	no
[fth_i]	fathom	fth	depth of water	no
[nmi_i]	nautical mile	n mile	length	no
[kn_i]	knot	kn	velocity	no
[sin_i]	square inch	In2	area	no
[sft_i]	square foot	ft2	area	no
[syd_i]	square yard	yd2	area	no
[cin_i]	cubic inch	In3	volume	no
[cft_i]	cubic foot	ft3	volume	no
[cyd_i]	cubic yard	yd3	volume	no
[bf_i]	board foot	fbm	volume	no
[cr_i]	cord	cord	volume	no
[mil_i]	mil	mil	length	no
[cml_i]	circular mil	cmil	area	no
[hd_i]	hand		height of horses	no

Older U.S. "survey" lengths NOTE also called “statute” lengths
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[ft_us]	foot	ft (US survey)	length	no
[yd_us]	yard		length	no
[in_us]	inch		length	no
[rd_us]	rod		length	no
[ch_us]	Gunter's chain, Surveyor's chain		length	no
[lk_us]	link for Gunter's chain		length	no
[rch_us]	Ramden's chain, Engineer's chain		length	no
[rlk_us]	link for Ramden's chain		length	no
[fth_us]	fathom		length	no
[fur_us]	furlong		length	no
[mi_us]	mile	mi (US survey)	length	no
[acr_us]	acre		area	no
[srd_us]	square rod		area	no
[smi_us]	square mile	Mi2 (US survey)	area	no
[sct]	section		area	no
[twp]	township		area	no
[mil_us]	mil		length	no

British Imperial lengths
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[in_br]	inch		length	no
[ft_br]	foot		length	no
[rd_br]	rod		length	no
[ch_br]	Gunter's chain		length	no
[lk_br]	link for Gunter's chain		length	no
[fth_br]	fathom		length	no
[pc_br]	pace		length	no
[yd_br]	yard		length	no
[mi_br]	mile		length	no
[nmi_br]	nautical mile		length	no
[kn_br]	knot		velocity	no
[acr_br]	acre		area	no

U.S. volumes NOTE Including so-called “dry measures”
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[gal_us]	Queen Anne's wine gallon		fluid volume	no
[bbl_us]	barrel	barrel (US)	fluid volume	no
[qt_us]	quart	liq qt (US)	fluid volume	no
[pt_us]	pint	liq pt (US)	fluid volume	no
[gil_us]	gill	gi (US)	fluid volume	no
[foz_us]	fluid ounce	fl oz (US)	fluid volume	no
[fdr_us]	fluid dram		fluid volume	no
[min_us]	minim		fluid volume	no
[crd_us]	cord		fluid volume	no
[bu_us]	bushel		dry volume	no
[gal_wi]	historical winchester gallon		dry volume	no
[pk_us]	peck		dry volume	no
[dqt_us]	dry quart		dry volume	no
[dpt_us]	dry pint		dry volume	no
[tbs_us]	tablespoon		volume	no
[tsp_us]	teaspoon		volume	no
[cup_us]	cup		volume	no
[foz_m]	metric fluid ounce		fluid volume	no
[cup_m]	metric cup		volume	no
[tsp_m]	metric teaspoon		volume	no
[tbs_m]	metric tablespoon		volume	no

British Imperial volumes
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[gal_br]	gallon	gal (UK)	volume	no
[pk_br]	peck	pk (UK)	volume	no
[bu_br]	bushel	bushel (UK)	volume	no
[qt_br]	quart	qt (UK)	volume	no
[pt_br]	pint	pt (UK)	volume	no
[gil_br]	gill	gi (UK)	volume	no
[foz_br]	fluid ounce	fl oz (UK)	volume	no
[fdr_br]	fluid dram		volume	no
[min_br]	minim		volume	no

Avoirdupois weights
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[gr]	grain		mass	no
[lb_av]	pound		mass	no
[oz_av]	ounce		mass	no
[dr_av]	dram		mass	no
[scwt_av]	short hundredweight, U.S. hundredweight		mass	no
[lcwt_av]	long hunderdweight, British hundredweight		mass	no
[ston_av]	short ton, U.S. ton		mass	no
[lton_av]	long ton, British ton		mass	no
[stone_av]	stone, British stone		mass	no

Troy weights
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[pwt_tr]	pennyweight		mass	no
[oz_tr]	ounce		mass	no
[lb_tr]	pound		mass	no

Units used in typesetting
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[lne]	line		length	no
[pnt]	point		length	no
[pca]	pica		length	no
[pnt_pr]	Printer's point		length	no
[pca_pr]	Printer's pica		length	no
[pied]	pied, French foot		length	no
[pouce]	pouce, French inch		length	no
[ligne]	ligne, French line		length	no
[didot]	didot, Didot's point		length	no
[cicero]	cicero, Didot's pica		length	no

B.3.6 Other legacy units

Legacy Units for Heat and Temperature
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
[degF]	degree Fahrenheit	°F	temperature	no
[degR]	degree Rankine	°R	temperature	no
[degRe]	degree Réaumur	°Ré	temperature	no
cal_[15]	calorie at 15 °C	cal15°C	energy	yes
cal_[20]	calorie at 20 °C	cal20°C	energy	yes
cal_m	mean calorie	calm	energy	yes
cal_IT	international table calorie	calIT	energy	yes
cal_th	thermochemical calorie	calth	energy	yes
cal	calorie	cal	energy	yes
[Cal]	nutrition label Calories	Cal	energy	no
[Btu_39]	British thermal unit at 39 °F	Btu39°F	energy	no
[Btu_59]	British thermal unit at 59 °F	Btu59°F	energy	no
[Btu_60]	British thermal unit at 60 °F	Btu60°F	energy	no
[Btu_m]	mean British thermal unit	Btum	energy	no
[Btu_IT]	international table British thermal unit	BtuIT	energy	no
[Btu_th]	thermochemical British thermal unit	Btuth	energy	no
[BTU]	British thermal unit	btu	energy	no
[HP]	horsepower		power	no
TEX	tex	tex	linear mass density (of textile thread)	yes
[DEN]	Denier	den	linear mass density (of textile thread)	no

Units Used Predominantly in Clinical Medicine
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
m[H2O]	meter of water column	m H2O	pressure	yes
m[Hg]	meter of mercury column	m Hg	pressure	yes
[in_i'H2O]	inch of water column	in H2O	pressure	no
[in_i'Hg]	inch of mercury column	in Hg	pressure	no
[PRU]	peripheral vascular resistance unit	P.R.U.	fluid resistance	no
[wood'U]	Wood unit	Wood U.	fluid resistance	no
[diop]	diopter	dpt	refraction of a lens	no
[p'diop]	prism diopter	PD	refraction of a prism	no
%[slope]	percent of slope	%	slope	no
[mesh_i]	mesh		lineic number	no
[Ch]	Charrière, french	Ch	gauge of catheters	no
[drp]	drop	drp	volume	no
[hnsf'U]	Hounsfield unit	HF	x-ray attenuation	no
[MET]	metabolic equivalent	MET	metabolic cost of physical activity	no
[hp'_X]	homeopathic potency of decimal series (retired)	X	homeopathic potency (retired)	no
[hp'_C]	homeopathic potency of centesimal series (retired)	C	homeopathic potency (retired)	no
[hp'_M]	homeopathic potency of millesimal series (retired)	M	homeopathic potency (retired)	no
[hp'_Q]	homeopathic potency of quintamillesimal series (retired)	Q	homeopathic potency (retired)	no
[hp_X]	homeopathic potency of decimal hahnemannian series	X	homeopathic potency (Hahnemann)	no
[hp_C]	homeopathic potency of centesimal hahnemannian series	C	homeopathic potency (Hahnemann)	no
[hp_M]	homeopathic potency of millesimal hahnemannian series	M	homeopathic potency (Hahnemann)	no
[hp_Q]	homeopathic potency of quintamillesimal hahnemannian series	Q	homeopathic potency (Hahnemann)	no
[kp_X]	homeopathic potency of decimal korsakovian series	X	homeopathic potency (Korsakov)	no
[kp_C]	homeopathic potency of centesimal korsakovian series	C	homeopathic potency (Korsakov)	no
[kp_M]	homeopathic potency of millesimal korsakovian series	M	homeopathic potency (Korsakov)	no
[kp_Q]	homeopathic potency of quintamillesimal korsakovian series	Q	homeopathic potency (Korsakov)	no

Units used in Chemical and Biomedical Laboratories
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
eq	equivalents	eq	amount of substance	yes
osm	osmole	osm	amount of substance (dissolved particles)	yes
[pH]	pH	pH	acidity	no
g%	gram percent	g%	mass concentration	yes
[S]	Svedberg unit	S	sedimentation coefficient	no
[HPF]	high power field	HPF	view area in microscope	no
[LPF]	low power field	LPF	view area in microscope	no
kat	katal	kat	catalytic activity	yes
U	Unit	U	catalytic activity	yes
[iU]	international unit	IU	arbitrary	yes
[IU]	international unit	i.U.	arbitrary	yes
[arb'U]	arbitary unit	arb. U	arbitrary	no
[USP'U]	United States Pharmacopeia unit	U.S.P.	arbitrary	no
[GPL'U]	GPL unit		biologic activity of anticardiolipin IgG	no
[MPL'U]	MPL unit		biologic activity of anticardiolipin IgM	no
[APL'U]	APL unit		biologic activity of anticardiolipin IgA	no
[beth'U]	Bethesda unit		biologic activity of factor VIII inhibitor	no
[anti'Xa'U]	anti factor Xa unit		biologic activity of factor Xa inhibitor (heparin)	no
[todd'U]	Todd unit		biologic activity antistreptolysin O	no
[dye'U]	Dye unit		biologic activity of amylase	no
[smgy'U]	Somogyi unit		biologic activity of amylase	no
[bdsk'U]	Bodansky unit		biologic activity of phosphatase	no
[ka'U]	King-Armstrong unit		biologic activity of phosphatase	no
[knk'U]	Kunkel unit		arbitrary biologic activity	no
[mclg'U]	Mac Lagan unit		arbitrary biologic activity	no
[tb'U]	tuberculin unit		biologic activity of tuberculin	no
[CCID_50]	50% cell culture infectious dose	CCID50	biologic activity (infectivity) of an infectious agent preparation	no
[TCID_50]	50% tissue culture infectious dose	TCID50	biologic activity (infectivity) of an infectious agent preparation	no
[EID_50]	50% embryo infectious dose	EID50	biologic activity (infectivity) of an infectious agent preparation	no
[PFU]	plaque forming units	PFU	amount of an infectious agent	no
[FFU]	focus forming units	FFU	amount of an infectious agent	no
[CFU]	colony forming units	CFU	amount of a proliferating organism	no
[IR]	index of reactivity	IR	amount of an allergen calibrated through in-vivo testing using the Stallergenes® method.	no
[BAU]	bioequivalent allergen unit	BAU	amount of an allergen calibrated through in-vivo testing based on the ID50EAL method of (intradermal dilution for 50mm sum of erythema diameters	no
[AU]	allergen unit	AU	procedure defined amount of an allergen using some reference standard	no
[Amb'a'1'U]	allergen unit for Ambrosia artemisiifolia	Amb a 1 U	procedure defined amount of the major allergen of ragweed.	no
[PNU]	protein nitrogen unit	PNU	procedure defined amount of a protein substance	no
[Lf]	Limit of flocculation	Lf	procedure defined amount of an antigen substance	no
[D'ag'U]	D-antigen unit		procedure defined amount of a poliomyelitis d-antigen substance	no
[FEU]	fibrinogen equivalent unit		amount of fibrinogen broken down into the measured d-dimers	no
[ELU]	ELISA unit		arbitrary ELISA unit	no
[EU]	Ehrlich unit		Ehrlich unit	no

Levels NOTE Pseudo-units defined to express logarithms of ratios between two quantities of the same kind
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
Np	neper	Np	level	yes
B	bel	B	level	yes
B[SPL]	bel sound pressure	B(SPL)	pressure level	yes
B[V]	bel volt	B(V)	electric potential level	yes
B[mV]	bel millivolt	B(mV)	electric potential level	yes
B[uV]	bel microvolt	B(μV)	electric potential level	yes
B[10.nV]	bel 10 nanovolt	B(10 nV)	electric potential level	yes
B[W]	bel watt	B(W)	power level	yes
B[kW]	bel kilowatt	B(kW)	power level	yes

Miscellaneous Units
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
st	stere	st	volume	yes
Ao	Ångström	Å	length	no
b	barn	b	action area	no
att	technical atmosphere	at	pressure	no
mho	mho	mho	electric conductance	yes
[psi]	pound per sqare inch	psi	pressure	no
circ	circle	circ	plane angle	no
sph	spere	sph	solid angle	no
[car_m]	metric carat	ctm	mass	no
[car_Au]	carat of gold alloys	ctAu	mass fraction	no
[smoot]	Smoot		length	no
[m/s2/Hz^(1/2)]	meter per square seconds per square root of hertz		amplitude spectral density	no

Units used in Information Science and Technology
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
bit_s	bit	bits	amount of information	no
bit	bit	bit	amount of information	yes
By	byte	B	amount of information	yes
Bd	baud	Bd	signal transmission rate	yes

Examples for Non-Units
Symbol (c/s)	Display Name	Print Symbol	Kind of Quantity	Metric
{tot}	particles total count	tot.	number	no
{tbl}	tablets	tbl.	number	no
{rbc}	red blood cell count	R.B.C.	number	no
g.m/{H.B.}	gram meter per heartbeat	g·m/H.B.	proportional to ventricular stroke work	no
gf.m/{H.B.}	gram-force meter per heartbeat	gf·m/H.B.	ventricular stroke work	no
kg{wet'tis}	kilogram of wet tissue	kg(wet tissue)	mass	no
mg{creat}	milligram of creatinine	mg(creat.)	mass	no