# Gram

The **gram** (originally **gramme**;[1] SI unit symbol **g**) is a unit of mass in the International System of Units (SI) equal to one one thousandth of a kilogram.

Gram | |
---|---|

General information | |

Unit system | SI |

Unit of | Mass |

Symbol | g |

Conversions | |

1 g in ... | ... is equal to ... |

SI base units | 10^{−3} kilograms |

CGS units | 1 gram |

Imperial units U.S. customary | 0.0353 ounces |

Originally defined as of 1795 as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre [1 cm^{3}], and at the temperature of melting ice",[2] the defining temperature (~0 °C) was later changed to 4 °C, the temperature of maximum density of water.

However, by the late 19th century, there was an effort to make the base unit the kilogram and the gram a derived unit. In 1960, the new International System of Units defined a *gram* as one one-thousandth of a kilogram (i.e., one gram is 1×10^{−3} kg). The kilogram, as of 2019, is defined by the International Bureau of Weights and Measures from the fixed numerical value of the Planck constant (h), which is 6.62607015×10^{−34} kg⋅m^{2}⋅s^{−1}.[3][4]