Gram
The gram (originally gramme; SI unit symbol g) is a unit of mass in the International System of Units (SI) equal to one thousandth of a kilogram.
| gram | |
|---|---|
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 |
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", 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).