Si Units list

Si Units list

What is unit?

The term unit indicates the amount or magnitude of any quantity which is measurable. Different units are used to indicate different measurements of particular kind of quantities.

What is unit in Physics?

In physics, there are a lot of physical quantities which are measured to perform an experiment and a lot of physical quantities which form the basis of mathematical equations which govern laws of physics such as length, mass and many more. In order to measure such physical quantities, Appropriate units are made to measure them accurately.

What is SI unit?

The term SI stands for International system of units. This is the standard system of measurements of units which is used by all the countries to measure any physical quantities. It was made to resolve the issue of different units used by different countries to measure a particular physical quantity.

The SI unit system consists of seven fundamental physical quantities units and these are fundamental because any other physical quantity in physics can be derived from these quantities relations. Any Physical quantity unit which is derived from fundamental physical quantities is known as Derived units.

Also read -

  • NCERT Solutions for Class 11 Physics
  • NCERT Solutions for Class 12 Physics
  • NCERT Solutions for All Subjects

Fundamental Physical Quantities:

In physics, there are seven fundamental physical quantities which form the basis for deriving any other physical quantities. These seven fundamental physical quantities are listed as:

  1. Length
  2. Time
  3. Mass
  4. Electric current
  5. Luminous intensity
  6. Amount of substance
  7. Temperature.

Definition, Symbols and SI units List of Fundamental physical Quantities:

Below is the SI unit list chart indicating their definition, symbols along with their SI unit.

Quantity NameDefinitionSI UnitSymbol
LengthLength is defined as the distance between two points of any object.meterm
TimeTime is the sequence of events that occurred in nature.seconds
MassMass is defined as the total amount of matter present in a body.Kilograms
Electric currentElectric current is defined as the flow of electric charges inside a material.AmpereA
Luminous IntensityLuminous Intensity is the total amount of visible light emitted in a unit of time per unit of solid angle.CandelaCd
Amount of SubstanceThe measurement of the number of atoms or molecules inside a material is called Amount of substance.Molemol
TemperatureThe measurement of intensity of heat inside a body is called temperature.KelvinK

Define Derived Units.

In physics, other than these seven fundamental physical quantities, any physical quantity can be derived from the relationship between these fundamental physical quantities and hence, these quantities are called derived quantities and units of such quantities are known as derived units.

Some of the most common and used derived units are listed below with their definition, SI units and their symbols.

Quantity NameDefinitionSI unitsymbol
AreaIt’s the amount of space covered by an object in two dimensional planemeter squarem2
VolumeIt’s the amount of space covered by an object in three dimensional space.meter cubem3
VelocityVelocity is the ratio of distance covered by a body over time.meter per secondms-1
AccelerationAcceleration is the ratio of velocity of a body over time.meter per second squarems-2
ForceThe product between mass of a body and the acceleration produced in it is called Force.NewtonN
FrequencyThe number of oscillations of a body in one second is called frequency.HertzHz
WorkThe product of force applied on a body and the displacement covered by it is known as work done.JouleJ
PressurePressure is the ratio between force acting on a body to the area to which force is applied.PascalPa
PowerPower is defined as the ratio between work done by a body over a given period of time.WattsW
DensityDensity is defined as the ratio between mass and volume of a body.Kilogram per meter cubeKgm-3

These are some derived units and there are more, in brief other than those seven fundamental physical quantities every quantity which is measurable in physics will be derived from those seven fundamental physical quantities and their SI unit name and symbol is after the scientist who discovered a particular kind of physical quantity. For example, It was. Isaac Newton who gave the idea of force so, SI unit of force or derived unit of force is called Newton, named after S. Isaac Newton.

Different units for measurement of most used fundamental physical quantities other than SI base units:

In physics, a single physical quantity can be measured in many different units with respect to their SI units due to their very large numerical values sometimes, some of most used Fundamental physical quantities can also be measured in different units are listed as”


Since, The SI unit of length is meter and its symbol is m. Along with this unit, following are most common used units for the measurement of length are given in unit table as:

Name of unitSymbolRelation with SI unit of Length (m)


Since, The SI unit of time is second and its symbol is s. Along with this unit, following are most common used units for the measurement of time are given in unit table as:

Name of UnitSymbolRelation with SI unit of Time (s)


Since, The SI unit of mass is Kilogram and its symbol is Kg. Along with this unit, following are most common used units for the measurement of mass are given in unit table as:

Name of unitSymbolRelation with SI unit of Mass (Kg)

Advantages of SI units:

  1. From country to country, we don’t need to convert one unit of any physical quantity measured to another system of units, SI unit provide standard unit used by all countries in the scientific field. This is the most important advantage of using SI unit.
  2. Some physical quantities have very long expressions for their measurements of units, SI unit provide the special memorable symbols for each fundamental physical quantity SI units which are easy to represent the unit of measurement of any physical quantity.
  3. The fundamental physical quantities are used to determine units of measurements of other physical quantities known as derived units so, SI unit of fundamental physical quantities gives the advantage to derive any physical quantity SI unit.

Also check-

  • NCERT Exemplar Class 11th Physics Solutions
  • NCERT Exemplar Class 12th Physics Solutions
  • NCERT Exemplar Solutions for All Subjects