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/s^{2}  feet per second squared  ft/s^{2}  
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/m^{3}  
Angle  radian  rad  
Angular Acceleration  radian per second squared  rad/s^{2}  
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  m^{2}  square feet  ft^{2}  
Area Density  kilogram per square meter  kg/m^{2}  pound per square feet  lb/ft^{2}  
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/m^{3}  
Catalitic Efficiency  cubic meter per mole second  m^{3}/(mol.s)  
Compressibility  reciprocal pascal  Pa^{1}  reciprocal pound force per square inch  (lbf/in^{2})^{1}  
Concentration  molar  M  
Current Density  ampere per square meter  A/m^{2}  
Curvature  reciprocal meter  m^{1}  reciprocal feet  ft^{1}  
Density  kilogram per cubic meter  kg/m^{3}  pounds per cubic feet  lb/ft^{3}  
Diffusion Coefficient  square meter per second  m^{2}/s  square feet per second  ft^{2}/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/in^{2}  
Electric Capacitance  farad  F  
Electric Charge  coulomb  C  
Electric Charge Density  coulomb per cubic meter  C/m^{3}  
Electric Conductance  siemens  S  
Electric Conductivity  siemens per meter  S/m  
Electric Current  ampere  A  
Electric Current Density  ampere per square meter  A/m^{2}  
Electric Displacement Field  coulomb per square meter  C/m^{2}  
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/m^{2}  
Electric Inductance  henry  H  
Electric Potential Difference  volt  V  
Electric Resistance  ohm  Ω  
Electromotive Force  volt  V  
Electron Mobility  square meter per volt second  m^{2}/(V.s)  
Emf  volt  V  
Energy  joule  J  feet pound force  ft.lbf  
Energy Density  joule per cubic meter  J/m^{3}  pound force/feet^{2}  
Energy Flux Density  joule per square meter second  J/(m^{2}.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/m^{3}  feet per cubic feet  ft/ft^{3}  
Heat  joule  J  feet pound force  ft.lbf  
Heat Capacity  joule per kelvin  J/K  
Heat Flux Density  watt per square meter  W/m^{2}  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/m^{2}  pound force per feet second  lbf/(ft.s)  
Jerk  meter per second cubic  m/s^{3}  feet per second cubic  ft/s^{3}  
Jolt  meter per second cubic  m/s^{3}  feet per second cubic  ft/s^{3}  
Jounce  meter per second to the fourth  m/s^{4}  feet per second to the fourth  ft/s^{4}  
Kerna  gray  Gy  
Kinematic Viscosity  square meter per second  m^{2}/s  square feet per second  ft^{2}/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/m^{2}  
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/m^{3}  pound per cubic feet  lb/ft^{3}  
Mass Density  kilogram per cubic meter  kg/m^{3}  pound per cubic feet  lb/ft^{3}  
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  (m^{2})/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/m^{3}  
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.m^{2}  pound square feet  lb.ft^{2}  
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/m^{2}  
Potential Difference  volt  V  
Power  watt  W  feet pound force per second  ft.lbf/s  
Power Density  watt per cubic meter  W/m^{3}  pound force per square feet second  lbf/(ft^{2}.s)  
Pressure  pascal  Pa  pound force per square inch  lbf/in^{2}  
Quantity of Electricity  coulomb  C  
Radiance  watt per square meter steradian  W/(m^{2}.sr)  
Radiant Exposure  joule per square meter  J/m^{2}  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/s^{4}  feet per second to the fourth  ft/s^{4}  
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  m^{3}/kg  cubic feet per pound  ft^{3}/lb  
Spectral Intensity  watt per steradian meter  W/(sr.m)  
Spectral Irradiance  watt per cubic meter  W/m^{3}  pound force per square feet second  lbf/(ft^{2}.s)  
Spectral Power  watt per meter  W/m  pound force feet per square second  lbf.ft/s^{2}  
Spectral Radiance  watt per steradian cubic meter  W/(sr.m^{3})  
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/in^{2}  
Surface Density  kilogram per square meter  kg/m^{2}  pound per square feet  lb/ft^{2}  
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  m^{2}/s  square feet per second  ft^{2}/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  m^{3}  cubic feet  ft^{3}   Measuring cup  Pipette filler 
Volumetric Flow  cubic meter per second  m^{3}/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.