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.

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 systemSI
Unit ofMass
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 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.

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⋅m2⋅s−1.[3][4]

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