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This article is about the unit of mass. For other uses of "g" "gram" and "gramme", see Gram (disambiguation).
The mass of this pen cap is about 1 gram
The mass of this pen cap is about 1 gram
Unit information
Unit system SI derived unit
Unit of Mass
Symbol g 
Unit conversions
1 g in ... ... is equal to ...
   SI base units    10-3 kilograms
   CGS units    1 gram
   U.S. customary    0.0353 ounces

The gram (alternative British English spelling: gramme;[1] SI unit symbol: g) (Greek/Latin root grámma) is a metric system unit of mass.

Originally defined as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre, and at the temperature of melting ice"[2] (later 4 °C), a gram is now defined as one one-thousandth of the SI base unit, the kilogram, or 1×10−3 kg, which itself is defined as being equal to the mass of a physical prototype preserved by the International Bureau of Weights and Measures.

Symbol and abbreviations[edit]

The International System of Units (SI) unit symbol for the gram is "g" following the numeric value with a space, as in "640 g". While some authors use ad hoc abbreviations, this creates confusion. For example, the use of abbreviations such as "gm", "Gm", or "GM" for grams could potentially lead to serious errors in health-care settings where accidentally transposing "gm" to "mg" (milligrams) could result in a 1,000 times dosage error. It is therefore important to use "g" as specified in the SI standard to avoid confusion or misunderstanding.

A bigger mistake is using the abbreviation "gr" for grams. The symbol "gr" stands for grains.[citation needed]


It was the base unit of mass in the original French metric system and the later centimetre-gram-second (CGS) system of units. The word originates from Late Latin gramma – a small weight.


The gram is today the most widely used unit of measurement for non-liquid ingredients in cooking and grocery shopping worldwide.

Most standards and legal requirements for nutrition labels on food products require relative contents to be stated per 100 g of the product, such that the resulting figure can also be read as a percentage.

Conversion factors[edit]


See also[edit]


  1. ^ "Weights and Measures Act 1985 (c. 72)". The UK Statute Law Database. Office of Public Sector Information. Retrieved 2011-01-26. "§92." 
  2. ^ Décret relatif aux poids et aux mesures, 1795
  3. ^ "Circulating Coin Designs". Japan Mint. Retrieved 7 March 2010. 

External links[edit]