In SI, there are seven base ( fundamental ) units and two supplementary units.

#### Base unit

Physical quantity | Unit | Symbol |
---|---|---|

Mass | Kilogram | kg |

Length | Metre | m |

Time | Second | s |

Temperature | Kelvin | K |

Electric current | Ampere | A |

Luminous intensity | Candela | cd |

Quantity of matter | Mole | mol |

#### Supplementary units

Physical quantity | Unit | Symbol |
---|---|---|

Plane angle | Radian | rad |

Solid angle | Steradian | sr |

### Conversion factor

#### Conversion of length

- 1 centimetre = 10
^{-2}metre - 1 millimetre = 10
^{-3}metre - 1 micrometre = 10
^{-6}metre - 1 nanometre = 10
^{-9}metre - 1 angstrom= 10
^{-10}metre - 1 fermi = 10
^{-15}metre - 1 kilometre = 10
^{3}metre - 1 austronomical unit = 1AU=1.496 × 10
^{11}metre - 1 light year = 1 ly = 9.461 ×10
^{15}metre - 1 mile = 1.609 ×10
^{3}metre - 1 yard = 0.9144 metre
- 1 inch = 0.0254 metre

#### Conversion of time

- 1 mili second= 10
^{-3}second - 1 micro second = 10
^{-6}second - 1 neno second = 10
^{-9}second - 1 hour = 60 minute = 3600 second
- 1 day = 24 hours =86400 second
- 1 year = 365 day = 3.156× 10
^{7}second - 1 sec = 10
^{-8}second

#### Conversion of mass

- 1 gram = 10
^{-3}kg - 1 quintal = 100 kg
- 1 tonne = 1000 kg
- 1 slug = 14.59 kg
- 1 Chandersekhar limit = 1.4 × mass of sun = 2.8 × 10
^{30}kg - 1 atomic mass unit = 1u = 1.66×10
^{-10}