# The International System of Units

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## Length

Basic unit is the meter (m), which equals 39.37 in.
Common Multiples and Subdivisions | |

kilometer (km) | 10^{3} m |

decimeter (dm) | 10^{-1} m |

centimeter (cm) | 10^{-2} m |

millimeter (mm) | 10^{-3} m |

micrometer (µm)* | 10^{-6} m |

nanometer (nm) | 10^{-9} m |

angstrom (Å) | 10^{-10} m |

*Also called the micron (µ)
## Mass

Basic unit is the gram (g).
Common Multiples and Subdivisions | |

kilogram (kg) | 10^{3} g (2.2 lb) |

centigram (cg) | 10^{-2} g |

milligram (mg) | 10^{-3} g |

microgram (µg) | 10^{-6} g |

nanogram (ng) | 10^{-9} g |

picogram (pg) | 10^{-12} g |

## Volume

Basic unit is the **liter**, which equals 1 cubic decimeter, dm^{3} (1.06 quart). A liter of water at its maximum density weighs almost 1 kg. Therefore, 1 ml (= 10^{-3} liter) of water weighs, for all practical purposes, 1 g. One cubic centimeter (cm^{3} or cc) is 10^{-3} dm^{3}. Therefore, it is equal to 1 ml, and the units **ml** and **cc** are used interchangeably.
## Temperature

Basic unit is the Celsius (formerly known as centigrade) degree, ^{o}C. 0^{o}C is the freezing point of water; 100^{o}C is the boiling point of water. To convert from ^{o}C to ^{o}F (Fahrenheit) or vice versa: ^{o}F - 32 = 9/5 ^{o}C.
## Useful Equivalents

- Length
- 1 inch = 2.54 cm

- Mass
- 1 oz = 28.35 g

1 lb = 453.6 g

- Volume
- 1 U.S. fluid oz = 29.57 ml

1 U.S. liquid qt = 0.946 liter (l)

- Pressure
- 1 pound per square inch (psi) = 6.89 kilopascals (kPa)

- Radiation dose
- 1 millisievert (mSv) = 100 millirems (mrem)

## Some Useful Constants and Conversion Factors

The gas constant: **R** = 2 cal / [(mole)(°K)]

The Faraday constant: **F** = 23,062 cal / [(mole)(volt)]

The natural logarithm, **ln**, = (2.303)(log_{10})

13 February 2012