| gram | |
|---|---|
.jpg) The mass of this pen cap is about 1 gram. A weight scale such as this can give an accurate reading of mass for many objects (see Weight vs. mass). | |
| 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 | 0.0352740 ounces |
| Atomic mass units | 6.02214076×1023 Da |
The gram (originally gramme;[1] SI unit symbol g) is a unit of mass in the International System of Units (SI) equal to one thousandth of a kilogram.
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 cm3], 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.
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).[3][4]
- ^ "Weights and Measures Act 1985 (c. 72)". The UK Statute Law Database. Office of Public Sector Information. Archived from the original on 12 September 2008. Retrieved 26 January 2011.
§92.
- ^ "Décret relatif aux poids et aux mesures" (in French). 1795. Archived from the original on 25 February 2013.
- ^ Draft Resolution A "On the revision of the International System of units (SI)" to be submitted to the CGPM at its 26th meeting (2018) (PDF), archived from the original (PDF) on 29 April 2018, retrieved 17 May 2020
- ^ Decision CIPM/105-13 (October 2016) Archived 24 August 2017 at the Wayback Machine. The day is the 144th anniversary of the Metre Convention.