# 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 QuantitiesMetric UnitsSymbolImperial UnitsSymbolInstrument
Absorbed DosegrayGy
Absorbed Dose Rategray per secondGy/s
Accelerationmeter per second squaredm/s2feet per second squaredft/s2
Actionjoule secondJ.sfeet pound force secondft.lbf.s
Amount of Substancemolemol
Amount of Substance Concentrationmole per cubic metermol/m3
Angular Momentumnewton meter secondN.m.spound force feet secondlbf.ft.s
Areasquare meterm2square feetft2
Area Densitykilogram per square meterkg/m2pound per square feetlb/ft2
- Capacitor tester
Catalitic Activitykatalkat
Catalitic Activity Concentrationkatal per cubic meterkat/m3
Catalitic Efficiencycubic meter per mole secondm3/(mol.s)
Compressibilityreciprocal pascalPa-1reciprocal pound force per square inch(lbf/in2)-1
ConcentrationmolarM
Current Densityampere per square meterA/m2
Curvaturereciprocal meterm-1reciprocal feetft-1
Densitykilogram per cubic meterkg/m3pounds per cubic feetlb/ft3
Diffusion Coefficientsquare meter per secondm2/ssquare feet per secondft2/s
Distancemetermfeetft- tape measure
- laser measure
- range finder
Dynamic Viscositypascal secondPa.spound force second per square inchlbf.s/in2
Electric ChargecoulombC
Electric Charge Densitycoulomb per cubic meterC/m3
Electric ConductancesiemensS
Electric Conductivitysiemens per meterS/m
Electric CurrentampereA
Electric Current Densityampere per square meterA/m2
Electric Displacement Fieldcoulomb per square meterC/m2
Electric Field Intensitynewton per coulombN/C
Electric Field Strengthvolt per meterV/m- EMF meter
Electric Flux Densitycoulomb per square meterC/m2
Electric InductancehenryH
Electric Potential DifferencevoltV
Electric ResistanceohmΩ
Electromotive ForcevoltV
Electron Mobilitysquare meter per volt secondm2/(V.s)
EmfvoltV
EnergyjouleJfeet pound forceft.lbf
Energy Densityjoule per cubic meterJ/m3pound force/feet2
Energy Flux Densityjoule per square meter secondJ/(m2.s)pound force per feet secondlbf/(ft.s)
Entropyjoule per kelvinJ/K
Equivalent DosesievertSv- Geiger counter
Exposurecoulomb per kilogramC/kg
ForcenewtonNpound forcelbf
FrequencyhertzHzcycles per secondcycles/s
Frequency DriftHertz per secondHz/s
Fuel Efficiencymeter per cubic meterm/m3feet per cubic feetft/ft3
HeatjouleJfeet pound forceft.lbf
Heat Capacityjoule per kelvinJ/K
Heat Flux Densitywatt per square meterW/m2pound force per feet secondlbf/(ft.s)
Illuminanceluxlx
ImpedanceohmΩ
Impulsenewton secondN.spound force secondlbf.s
InductancehenryH
Irradiancewatt per square meterW/m2pound force per feet secondlbf/(ft.s)
Jerkmeter per second cubicm/s3feet per second cubicft/s3
Joltmeter per second cubicm/s3feet per second cubicft/s3
Jouncemeter per second to the fourthm/s4feet per second to the fourthft/s4
KernagrayGy
Kinematic Viscositysquare meter per secondm2/ssquare feet per secondft2/s
Lengthmetermfeetft- tape meausre
- laser measure
- range finder
Linear Charge Densitycoulomb per meterC/m
Linear Mass Densitykilogram per meterkg/mpound per feetlb/ft
Luminancecandela per square metercd/m2
Luminous Efficacylumen per wattlm/W
Luminous Energylumen secondlm.s
Luminous Exposurelux secondlx.s
Luminous Fluxlumenlm
Luminous Intensitycandelacd
Magnetic Dipole Momentjoule per teslaJ/T
Magnetic Field Strengthampere per meterA/m- EMF meter
- Gauss meter
Magnetic FluxweberWb
Magnetic Flux DensityteslaT- Gauss meter
Magnetic InductionteslaT
Magnetic Momentweber meterWb.m
Magnetic Permeabilityhenry per meterH/m
Magnetic Reluctancereciprocal henryH-1
Magnetic Rigiditytesla meterT.m
Magnetic Suspectibilitymeter per henrym/H
Magnetic Vector Potentialweber per meterWb/m
Magnetizationampere per meterA/m
Masskilogramkgpoundlb- Scale
Mass Concentrationkilogram per cubic meterkg/m3pound per cubic feetlb/ft3
Mass Densitykilogram per cubic meterkg/m3pound per cubic feetlb/ft3
Mass Flow Ratekilogram per secondkg/spound per secondlb/s
Mass Fractionkilogram per kilogramkg/kgpound per poundlb/lb
Molalitymole per kilogrammol/kg
Molar Conductivitysquare meter per mole(m2)/mol
Molar Energyjoule per moleJ/mol
Molar Entropyjoule per mole kelvinJ/(mol.K)
Molar Heat Capacityjoule per mol kelvinJ/(mol.K)
Molar Masskilogram per molekg/mol
Molaritymol per cubic metermol/m3
Mole Fractionmole per molemol/mol
Moment of Forcenewton meterN.mpound force feetlbf.ft
Moment of Inertiakilogram square meterkg.m2pound square feetlb.ft2
Momentumnewton secondN.spound force secondlbf.s
Optical Powerreciprocal meterm-1reciprocal feetft-1
Permeabilityhenry per meterH/m
Polarization Densitycoulomb per square meterC/m2
Potential DifferencevoltV
PowerwattWfeet pound force per secondft.lbf/s
Power Densitywatt per cubic meterW/m3pound force per square feet secondlbf/(ft2.s)
PressurepascalPapound force per square inchlbf/in2
Quantity of ElectricitycoulombC
Radiant Exposurejoule per square meterJ/m2pound force per feetlbf/ft
Radiant FluxwattWpound force feet per secondlbf.ft/s
ReactanceohmΩ
Refractive Indexone1
Relative Permeabilityone1
Resistivityohm meterΩ.m
Snapmeter per second to the fourthm/s4feet per second to the fourthft/s4
Spatial Frequencyreciprocal meterm-1reciprocal feetft-1
Specific Angular Momentumnewton meter second per kilogramN.m.s/kgpound force feet second per poundlbf.ft.s/lb
Specific Energy (Imparted)grayGy
Specific Energy (Imparted)joule per kilogramJ/kgpound force feet per poundlbf.ft/lb
Specific Entropyjoule per kilogram kelvinJ/(kg.K)
Specific Heat Capacityjoule per kilogram kelvinJ/(kg.K)
Specific Volumecubic meter per kilogramm3/kgcubic feet per poundft3/lb
Spectral Irradiancewatt per cubic meterW/m3pound force per square feet secondlbf/(ft2.s)
Spectral Powerwatt per meterW/mpound force feet per square secondlbf.ft/s2
Speedmeter per secondm/sfeet per secondft/s- Speedometer
- Tachometer
Stiffnessnewton per meterN/mpound force per feetlbf/ft
StresspascalPapound force per square inchlbf/in2
Surface Densitykilogram per square meterkg/m2pound per square feetlb/ft2
Surface Tensionnewton per meterN/mpound force per feetlbf/ft
TemperaturekelvinK- Thermometer
Thermal Conductivitywatt per meter kelvinW/(m.K)
Thermal Diffusitysquare meter per secondm2/ssquare feet per secondft2/s
Thermal Expansion Coefficientreciprocal kelvinK-1
Thermal Resistancekelvin per wattK/W
Thicknessmeterminch, mil- Dial caliper
- Digital caliper
- Vernier caliper
- Feeler gauge
- Paint thickness meter
Timeseconds- Watch
- Atomic clock
- Hourglass
- Hour meter
Torquenewton meterN.mpound force feetlbf.ft
Velocitymeter per secondm/sfeet per secondft/s- Speedometer
- Tachometer
- Anemometer
VoltagevoltV- Voltmeter
- Multimeter
Volumecubic meterm3cubic feetft3- Measuring cup
- Pipette filler
Volumetric Flowcubic meter per secondm3/s- Flow meter
Wavenumberreciprocal meterm-1reciprocal feetft-1
WeightnewtonNpound forcelbf
WorkjouleJfeet pound forceft.lbf
Yanknewton per secondN/spound force per secondlbf/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.