158 Physical Quantities and Units

Physical quantities and units are among the basic things in measurement that you have to know. When learning about physics, engineering, instrumentation, and metrology, you are not far from physical quantities and units.

In regard to buying a measuring device, it goes the same thing, physical quantities and units are the most fundamental thing you have to acknowledge. You have to know what physical quantity that the device measures and what unit it uses. Then you could observe further its measuring range, resolution, accuracy, etc.

So, What are Physical Quantities and Units?

A physical quantity is the physical property of an object that can be expressed (measurable) in a number/value and a unit. These two components (value and unit) are unseparated.

For example, a retractable tape measuring tool measures a steel bar, and its length is 25 feet. The steel bar is the object. It has a physical quantity of length. The length is expressed in a value of 25. This value is obtained from a measurement using a tape measure. The tape measure expresses the value (25) in a unit of feet. There are many measuring tools for the length that behave the same thing as this tape measure.

Aside from that, an object can have more than one physical quantity. For example, a magnet has some physical quantities such as mass, magnetic strength, dimension (volume), hardness, etc.

In some cases, an object has only value but no direction. This is called a scalar quantity. Length, volume, energy, mass, and time are the example of scalar quantities. On the other hand, the quantities can have value and direction. It’s called a vector quantity. Velocity, acceleration, force, and current are the example of vector quantities.

There are various physical quantities. They can be expressed either in metric or imperial units. In this post, we enlist the 158 physical quantities and units, both from the base and the derived quantities.

Physical Quantities	Metric Units	Symbol	Imperial Units	Symbol	Instrument
Absorbed Dose	gray	Gy
Absorbed Dose Rate	gray per second	Gy/s
Acceleration	meter per second squared	m/s²	feet per second squared	ft/s²
Action	joule second	J.s	feet pound force second	ft.lbf.s
Activity of a Radionuclide	becquerel	Bq
Amount of Substance	mole	mol
Amount of Substance Concentration	mole per cubic meter	mol/m³
Angle	radian	rad
Angular Acceleration	radian per second squared	rad/s²
Angular Momentum	newton meter second	N.m.s	pound force feet second	lbf.ft.s
Angular Velocity	radian per second	rad/s
Area	square meter	m²	square feet	ft²
Area Density	kilogram per square meter	kg/m²	pound per square feet	lb/ft²
Avogadro Constant	reciprocal mole	mol^-1
Capacitance	farad	F			- Capacitance meter - Capacitor tester
Catalitic Activity	katal	kat
Catalitic Activity Concentration	katal per cubic meter	kat/m³
Catalitic Efficiency	cubic meter per mole second	m³/(mol.s)
Compressibility	reciprocal pascal	Pa^-1	reciprocal pound force per square inch	(lbf/in²)^-1
Concentration	molar	M
Current Density	ampere per square meter	A/m²
Curvature	reciprocal meter	m^-1	reciprocal feet	ft^-1
Density	kilogram per cubic meter	kg/m³	pounds per cubic feet	lb/ft³
Diffusion Coefficient	square meter per second	m²/s	square feet per second	ft²/s
Distance	meter	m	feet	ft	- tape measure - laser measure - range finder
Dynamic Viscosity	pascal second	Pa.s	pound force second per square inch	lbf.s/in²
Electric Capacitance	farad	F
Electric Charge	coulomb	C
Electric Charge Density	coulomb per cubic meter	C/m³
Electric Conductance	siemens	S
Electric Conductivity	siemens per meter	S/m
Electric Current	ampere	A
Electric Current Density	ampere per square meter	A/m²
Electric Displacement Field	coulomb per square meter	C/m²
Electric Field Intensity	newton per coulomb	N/C
Electric Field Strength	volt per meter	V/m			- EMF meter
Electric Flux Density	coulomb per square meter	C/m²
Electric Inductance	henry	H
Electric Potential Difference	volt	V
Electric Resistance	ohm	Ω
Electromotive Force	volt	V
Electron Mobility	square meter per volt second	m²/(V.s)
Emf	volt	V
Energy	joule	J	feet pound force	ft.lbf
Energy Density	joule per cubic meter	J/m³	pound force/feet²
Energy Flux Density	joule per square meter second	J/(m².s)	pound force per feet second	lbf/(ft.s)
Entropy	joule per kelvin	J/K
Equivalent Dose	sievert	Sv			- Geiger counter
Exposure	coulomb per kilogram	C/kg
Force	newton	N	pound force	lbf
Frequency	hertz	Hz	cycles per second	cycles/s
Frequency Drift	Hertz per second	Hz/s
Fuel Efficiency	meter per cubic meter	m/m³	feet per cubic feet	ft/ft³
Heat	joule	J	feet pound force	ft.lbf
Heat Capacity	joule per kelvin	J/K
Heat Flux Density	watt per square meter	W/m²	pound force per feet second	lbf/(ft.s)
Illuminance	lux	lx
Impedance	ohm	Ω
Impulse	newton second	N.s	pound force second	lbf.s
Inductance	henry	H
Irradiance	watt per square meter	W/m²	pound force per feet second	lbf/(ft.s)
Jerk	meter per second cubic	m/s³	feet per second cubic	ft/s³
Jolt	meter per second cubic	m/s³	feet per second cubic	ft/s³
Jounce	meter per second to the fourth	m/s⁴	feet per second to the fourth	ft/s⁴
Kerna	gray	Gy
Kinematic Viscosity	square meter per second	m²/s	square feet per second	ft²/s
Length	meter	m	feet	ft	- tape meausre - laser measure - range finder
Linear Charge Density	coulomb per meter	C/m
Linear Mass Density	kilogram per meter	kg/m	pound per feet	lb/ft
Luminance	candela per square meter	cd/m²
Luminous Efficacy	lumen per watt	lm/W
Luminous Energy	lumen second	lm.s
Luminous Exposure	lux second	lx.s
Luminous Flux	lumen	lm
Luminous Intensity	candela	cd
Magnetic Dipole Moment	joule per tesla	J/T
Magnetic Field Strength	ampere per meter	A/m			- EMF meter - Gauss meter
Magnetic Flux	weber	Wb
Magnetic Flux Density	tesla	T			- Gauss meter
Magnetic Induction	tesla	T
Magnetic Moment	weber meter	Wb.m
Magnetic Permeability	henry per meter	H/m
Magnetic Reluctance	reciprocal henry	H^-1
Magnetic Rigidity	tesla meter	T.m
Magnetic Suspectibility	meter per henry	m/H
Magnetic Vector Potential	weber per meter	Wb/m
Magnetization	ampere per meter	A/m
Magnetomotive Force	ampere radian	A.rad
Mass	kilogram	kg	pound	lb	- Scale
Mass Concentration	kilogram per cubic meter	kg/m³	pound per cubic feet	lb/ft³
Mass Density	kilogram per cubic meter	kg/m³	pound per cubic feet	lb/ft³
Mass Flow Rate	kilogram per second	kg/s	pound per second	lb/s
Mass Fraction	kilogram per kilogram	kg/kg	pound per pound	lb/lb
Molality	mole per kilogram	mol/kg
Molar Conductivity	square meter per mole	(m²)/mol
Molar Energy	joule per mole	J/mol
Molar Entropy	joule per mole kelvin	J/(mol.K)
Molar Heat Capacity	joule per mol kelvin	J/(mol.K)
Molar Mass	kilogram per mole	kg/mol
Molarity	mol per cubic meter	mol/m³
Mole Fraction	mole per mole	mol/mol
Moment of Force	newton meter	N.m	pound force feet	lbf.ft
Moment of Inertia	kilogram square meter	kg.m²	pound square feet	lb.ft²
Momentum	newton second	N.s	pound force second	lbf.s
Optical Power	reciprocal meter	m^-1	reciprocal feet	ft^-1
Permittivity	farad per meter	F/m
Permeability	henry per meter	H/m
Plane Angle	radian	rad
Polarization Density	coulomb per square meter	C/m²
Potential Difference	volt	V
Power	watt	W	feet pound force per second	ft.lbf/s
Power Density	watt per cubic meter	W/m³	pound force per square feet second	lbf/(ft².s)
Pressure	pascal	Pa	pound force per square inch	lbf/in²
Quantity of Electricity	coulomb	C
Radiance	watt per square meter steradian	W/(m².sr)
Radiant Exposure	joule per square meter	J/m²	pound force per feet	lbf/ft
Radiant Flux	watt	W	pound force feet per second	lbf.ft/s
Radiant Intensity	watt per steradian	W/sr
Radioactivity	becquerel	Bq
Reactance	ohm	Ω
Refractive Index	one	1
Relative Permeability	one	1
Resistivity	ohm meter	Ω.m
Snap	meter per second to the fourth	m/s⁴	feet per second to the fourth	ft/s⁴
Solid Angle	steradian	sr
Spatial Frequency	reciprocal meter	m^-1	reciprocal feet	ft^-1
Specific Angular Momentum	newton meter second per kilogram	N.m.s/kg	pound force feet second per pound	lbf.ft.s/lb
Specific Energy (Imparted)	gray	Gy
Specific Energy (Imparted)	joule per kilogram	J/kg	pound force feet per pound	lbf.ft/lb
Specific Entropy	joule per kilogram kelvin	J/(kg.K)
Specific Heat Capacity	joule per kilogram kelvin	J/(kg.K)
Specific Volume	cubic meter per kilogram	m³/kg	cubic feet per pound	ft³/lb
Spectral Intensity	watt per steradian meter	W/(sr.m)
Spectral Irradiance	watt per cubic meter	W/m³	pound force per square feet second	lbf/(ft².s)
Spectral Power	watt per meter	W/m	pound force feet per square second	lbf.ft/s²
Spectral Radiance	watt per steradian cubic meter	W/(sr.m³)
Speed	meter per second	m/s	feet per second	ft/s	- Speedometer - Tachometer
Stiffness	newton per meter	N/m	pound force per feet	lbf/ft
Stress	pascal	Pa	pound force per square inch	lbf/in²
Surface Density	kilogram per square meter	kg/m²	pound per square feet	lb/ft²
Surface Tension	newton per meter	N/m	pound force per feet	lbf/ft
Temperature	kelvin	K			- Thermometer
Temperature Gradient	kelvin per meter	K/m
Thermal Conductivity	watt per meter kelvin	W/(m.K)
Thermal Diffusity	square meter per second	m²/s	square feet per second	ft²/s
Thermal Expansion Coefficient	reciprocal kelvin	K^-1
Thermal Resistance	kelvin per watt	K/W
Thickness	meter	m	inch, mil		- Dial caliper - Digital caliper - Vernier caliper - Feeler gauge - Paint thickness meter
Time	second	s			- Watch - Atomic clock - Hourglass - Hour meter
Torque	newton meter	N.m	pound force feet	lbf.ft
Velocity	meter per second	m/s	feet per second	ft/s	- Speedometer - Tachometer - Anemometer
Voltage	volt	V			- Voltmeter - Multimeter
Volume	cubic meter	m³	cubic feet	ft³	- Measuring cup - Pipette filler
Volumetric Flow	cubic meter per second	m³/s			- Flow meter
Wavenumber	reciprocal meter	m^-1	reciprocal feet	ft^-1
Weight	newton	N	pound force	lbf
Work	joule	J	feet pound force	ft.lbf
Yank	newton per second	N/s	pound force per second	lbf/s

Last Thought

Learning about physical quantity can be an urgent thing. It guides you to know exactly what you are doing. For example, when measuring the radiation, you should know the physical quantities that you have to measure. If you just use the measuring device, and the device claims it measures radiation, in fact, it only measures the magnetic field, you get fooled. Indeed, you have to measure the magnetic field strength, electric field strength, and power density of the radio wave.

There are also biological and chemical quantities. These are another level of the topic that we hope to cover soon.

So, What are Physical Quantities and Units?

Last Thought

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