SI Base, Derived, and Other Units

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Table 3-10 lists additional units available in the COMSOL Multiphysics software regardless of the unit system in the model. If more than one name or symbol is available, use any of them, except when names contain more than one word or a hyphen. See also the tables with special units for other unit systems than the SI system; special units that are not listed in Table 3-10 are only available when using such non-SI unit systems.

Base quantity	Unit name	symbol
length	meter, metre*	m
mass	kilogram	kg
time	second	s
electric current	ampere	A
temperature	kelvin**	K
amount of substance	mole	mol
luminous intensity	candela	cd
* See About Editing Geometry Length and Angular Units **See About Temperature Units

Derived quantity	name	symbol
absorbed dose	gray	Gy
capacitance	farad	F
conductance	siemens	S
dose equivalent	sievert	Sv
electric charge	coulomb	C
electric resistance, impedance, reactance	ohm*	Ω
electric potential difference, voltage	volt	V
energy, work, heat	joule	J
force, weight	newton	N
frequency	hertz	Hz
inductance	henry	H
magnetic flux	weber	Wb
magnetic flux density, magnetic induction	tesla	T
plane angle	radian	rad
power	watt	W
pressure	pascal	Pa
* See the additional notes following the next table.

quantity	name	symbols	Value
acceleration	galileo	Gal	0.01 m/s2
acoustic impedance	rayl*	rayl, rayl_cgs	1 Pa·s/m (rayl), 10 Pa·s/m (rayl_cgs)
dimensionless value	percent	%	0.01
dimensionless value	partspermillion (parts per million)	ppm	10-6
dipole moment	debye	D	3.33564095·10-30 C·m
dynamic viscosity	poise	P	0.1 Pa·s
electric charge	amperehour	Ah	3600 C
energy	British thermal unit*	BTU, Btu	1055.05585 J
energy	calorie*	cal	4.184 J
energy	electronvolt	eV	1.6021765314·10-19 J
energy	erg	erg	10-7 J
energy	watthour	Wh	3600 J
force	dyne	dyn	10-5 N
force	kilopond*	kp, kpf	9.80665 N
force	poundal	pdl	0.138254954376 N
force	pound-force	lbf	4.4482216152605 N
frequency	rpm	RPM	1/60 Hz
length	angstrom	Å	10-10 m
length	inch	in	0.0254 m
length	foot	ft	0.3048 m
length	mile*	mi	1609.344 m
length	microinch	uin	0.0254·10-6 m
length	milliinch	mil, thou	0.0254·10-3 m
length	nautical mile*, nautimile	nmi	1852 m
length	yard	yd	0.9144 m
magnetic field strength	oersted	Oe	103/(4·π) A/m
magnetic flux density	gauss	G	10-4 T
mass	atomic mass unit, dalton	u, amu, Da	1.660538782·10-27 kg
mass	gram	g	0,001 kg
mass	ounce	oz	0.028349523 kg (1/16 lb)
mass	pound, pound-mass	lb, lbm	0.45359237 kg
mass	stone	st	6.35029318 kg
mass	slug	slug	approx. 14.5939 kg
mass	ton, tonne	t	1000 kg
molar concentration (molarity)	molar	M	1000 mol/m3
permeability	millidarcy*	mD	9.869233·10-16 m2
plane angle	arcminute	arcmin	π/10800
plane angle	arcsecond	arcsec	π/648000
plane angle	degree	deg	π/180
pressure	atmosphere	atm	101325 Pa
pressure	bar	bar	100000 Pa
pressure	barye	ba	0.1 Pa
pressure	kilopound per square inch*	ksi	6.894757·106 Pa (1000 psi)
pressure	psi	psi	6.894757·103 Pa
pressure	torr	Torr, mmHg	133.322 Pa
pressure	inches water*	inAq, inH2O	249.089 Pa
pressure	millimeters water*	mmH2O	9.0866 Pa
speed	mph, MPH	mph	0.44704 m/s
speed	knot*	knot	1852 km/h (approx. 0.614 m/s)
temperature	Celsius**	degC	T+273.15
temperature	Fahrenheit**	degF	5/9·T+459.67
temperature	Rankine**	R, Ra	5/9·T
time	year*	a, yr	31556952 s
time	day	d	86400 s
time	hour	h	3600 s
time	minute	min	60 s
volume	fluid ounce*	fl_oz	2.8413063·10-5 m3
volume	gallon*	gal	0.003785411784 m3
volume	imperialgallon	impgal	0.00454609 m3
volume	liter, litre	L, l	0.001 m3
volume	pint*	pt	0.000473176473 m3
volume	quart*	qt	0.000946352946 m3
volumetric flow rate	cubic feet per minute	CFM, cfm	4.719474·10-4 m3/s
* See the additional notes following this table. ** See About Temperature Units

Additional Notes about units in Table 3-9 and Table 3-10
Unit Name	Note
British thermal unit	An energy unit defined as the amount of heat required to raise the temperature of one pound (pound-mass) of water by one degree from 60° to 61° Fahrenheit at a constant pressure of one atmosphere. Refer to the British thermal unit using the symbol only (Btu or BTU): for example, 0.28[Btu/(hindegF)] for a thermal conductivity.
calorie	Small calorie or gram calorie, which equals 4.184 J. A large calorie or kilogram calorie is 1000 calories (4.184 kJ). Use [kcal] for large calories.
fluid ounce	The fluid ounce is equal to 1/160 of an imperial gallon: 2.8413063·10-5 m3; that is, an imperial fluid ounce. You can refer to this unit using fluid_ounce (as the unit) or fl_oz (as the symbol).
kilopond	The kilopond (kp) or kilogram-force (kpf) is a gravitational metric unit of force. Refer to this unit using kilopond, kp, or kpf only.
kilopound per square inch	The kilopound per square inch (ksi) is a scaled pressure unit derived from psi (1 ksi is equal to 1000 psi). Refer to this unit using the symbol only (ksi).
millidarcy (mD)	Widely used for permeability in petroleum engineering. Typical values for the permeability of porous media are in the range of a few to a few hundred mD. The symbol D represents the debye, a unit for the magnetic dipole moment, and not the darcy unit.
mile	The international statute mile, which equals 1609.344 m.
nautimile	The nautical mile equals 1852 m.
ohm	To declare the SI unit for electric resistance, ohm, use [ohm]. The COMSOL Multiphysics software then displays this as Ω .
inches water	The value of 1 inch of water is defined as the pressure exerted by one inch of water for a pure water density of 1000 kg/m3 at 4 degrees Celsius and standard gravity of 9.80665 m/s2. Refer to this unit using the symbol only (inH2O or inAq).
millimeters water	Millimeters water or millimeters, water gauge, is defined as the pressure exerted by one millimeter of water for a pure water density of 1000 kg/m3 at 4 degrees Celsius and standard gravity of 9.80665 m/s2. Refer to this unit using the symbol only (mmH2O).
knot	The same as nautical miles per hour.
year	A Gregorian year, which equals 365.2425 days.
gallon (gal)	This is the U.S. liquid gallon which equals 0.003785411784 m3; the Imperial (UK) gallon (imperialgallon, impgal) is equal to 0.00454609 m3.
pint and quart	The U.S. liquid pint and U.S. liquid quart, respectively.
rayl and rayl_cgs	The rayl (Rayl, Rayleigh) is a unit for the specific acoustic impedance. There are two variants, rayl, for MKS units, and rayl_cgs, for CGS units, where 1 rayl_cgs = 10 rayl. Refer to this unit the symbols only (rayl and rayl_cgs).