All physical quantities can be defined in terms of few fundamental physical quantities like Length, Mass and Time. The unit of these fundamental physical quantities or basic quantities are independent of each other and no one can further resolve it into any other unit. There are 7 basic or fundamental physical quantities. They are Length, Mass, Time, Temperature, Electric Current, Luminous Intensity and Amount of Substance.
| Fundamental Physical Quantities | SI Unit | Symbol | Dimensional Formula |
| Length | metre | m | M0L1T0 |
| Mass | kilogram | kg | M1L0T0 |
| Time | second | s | M0L0T1 |
| Temperature | kelvin | K or θ | M0L0T0θ or M0L0T0K1 |
| Electric Current | ampere | A | M0L0T0A1 |
| Luminous Intensity | candela | Cd | M0L0T0Cd1 |
| Amount of Substance | mole | mol | M0L0T0mol1 |
| Supplementary units | SI Unit | Symbol | Dimensional Formula |
| Plane Angle | radian | rad | Dimensionless |
| Solid Angle | steradian | Sr | Dimensionless |