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Gram (pen cap on scale).jpg
The mass of this pen cap is about 1 gram
General information
Unit system UCUM base unit and CGS unit
Unit of Mass
1 g in ...... is equal to ...
    SI base units    10−3 kilograms
    CGS units    1 gram
    Imperial units
U.S. customary
   0.0353 ounces

The gram (alternative spelling: gramme; [1] SI unit symbol: g) 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 [1 cm3 ], and at the temperature of melting ice" [2] (later at 4 °C, the temperature of maximum density of water). However, in a reversal of reference and defined units, a gram is now defined as one thousandth of the SI base unit, the kilogram, or 1×10−3 kg, which itself is defined by the International Bureau of Weights and Measures, not in terms of grams, but by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 kg⋅m2⋅s−1. [3] [4]

Official SI symbol

The only unit symbol for gram that is recognised by the International System of Units (SI) is "g" following the numeric value with a space, as in "640 g" to stand for "640 grams" in the English language. The SI does not support the use of abbreviations such as "gr" (which is the symbol for grains), [5] :C-19 "gm" ("g⋅m" is the SI symbol for gram-metre) or "Gm" (the SI symbol for gigametre).


The word gramme was adopted by the French National Convention in its 1795 decree revising the metric system as replacing the gravet introduced in 1793. Its definition remained that of the weight (poids) of a cubic centimetre of water. [6] [7]

French gramme was taken from the Late Latin term gramma. This word—ultimately from Greek γράμμα (grámma), "letter"—had adopted a specialised meaning in Late Antiquity of "one twenty-fourth part of an ounce" (two oboli), [8] corresponding to about 1.14 modern grams. This use of the term is found in the carmen de ponderibus et mensuris ("poem about weights and measures") composed around 400 AD. [lower-alpha 1] There is also evidence that the Greek γράμμα was used in the same sense at around the same time, in the 4th century, and survived in this sense into Medieval Greek, [10] while the Latin term did not remain current in Medieval Latin and was recovered in Renaissance scholarship. [lower-alpha 2]

The gram was the fundamental unit of mass in the 19th-century centimetre–gram–second system of units (CGS). The CGS system co-existed with the MKS system of units, first proposed in 1901, during much of the 20th century, but the gram has been displaced by the kilogram as the fundamental unit for mass when the MKS system was chosen for the SI base units in 1960.


The gram is today the most widely used unit of measurement for non-liquid ingredients in cooking and grocery shopping worldwide. [11] [12]

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 by weight.

Conversion factors


See also


  1. The date and authorship of this Late Latin didactic poem are both uncertain; it was attributed to Priscian but is now attributed to Rem(m)ius Favinus/Flav(in)us. [9] The poem's title is reflected in the French phrase poids et mesures ("weights and mesures") in the title of the 1795 National Convention decree, Décret relatif aux poids et aux mesures that introduced the gram, and indirectly in the name of the General Conference on Weights and Measures responsible for the modern definition of the metric units.
  2. In the Renaissance, the carmen de ponderibus et mensuris was received as a work of the 1st-century grammarian Remmius Palaemon edited in 1528 by Johann Setzer of Hagenau, together with works by Celsius, Priscian and Johannes Caesarius; Aurelij Cornelij Celsi, De re medica, libri octo eruditissimi. Q. Sereni Samonici Praecepta medica, uersibus hexametris. Q. Rhemnij Fannij Palaemonis, De ponderibus [et] mensuris, liber rarus [et] utilissimus

Related Research Articles

Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors.

Kilogram SI unit of mass

The kilogram is the base unit of mass in the International System of Units (SI), the current metric system, having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo in everyday speech.

Litre Unit of volume

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Metre Convention 1875 international treaty

The Metre Convention, also known as the Treaty of the Metre, is an international treaty that was signed in Paris on 20 May 1875 by representatives of 17 nations. The treaty created the International Bureau of Weights and Measures (BIPM), an intergovernmental organization under the authority of the General Conference on Weights and Measures (CGPM) and the supervision of the International Committee for Weights and Measures (CIPM), that coordinates international metrology and the development of the metric system.

The pound or pound-mass is a unit of mass used in the imperial, United States customary and other systems of measurement. Various definitions have been used; the most common today is the international avoirdupois pound, which is legally defined as exactly 0.45359237 kilograms, and which is divided into 16 avoirdupois ounces. The international standard symbol for the avoirdupois pound is lb; an alternative symbol is lbm, #, and or ″̶ (specifically for the apothecaries' pound).

International System of Units Modern form of the metric system

The International System of Units is the modern form of the metric system. It is the only system of measurement with an official status in nearly every country in the world. It comprises a coherent system of units of measurement starting with seven base units, which are the second, metre, kilogram, ampere, kelvin, mole, and candela. The system allows for an unlimited number of additional units, called derived units, which can always be represented as products of powers of the base units. Twenty-two derived units have been provided with special names and symbols. The seven base units and the 22 derived units with special names and symbols may be used in combination to express other derived units, which are adopted to facilitate measurement of diverse quantities. The SI system also provides twenty prefixes to the unit names and unit symbols that may be used when specifying power-of-ten multiples and sub-multiples of SI units. The SI is intended to be an evolving system; units and prefixes are created and unit definitions are modified through international agreement as the technology of measurement progresses and the precision of measurements improves.

Avogadro constant Fundamental physical constant (symbols: L,Nᴀ) representing the molar number of entities

The Avogadro constant (NA or L) is the proportionality factor that relates the number of constituent particles (usually molecules, atoms or ions) in a sample with the amount of substance in that sample. Its SI unit is the reciprocal mole, and it is defined as NA = 6.02214076×1023 mol−1. It is named after the Italian scientist Amedeo Avogadro.Although this is called Avogadro's constant (or number), he is not the chemist who determined its value. Stanislao Cannizzarro explained this number four years after Avogadro's death while at the Karlsruhe Congress in 1860.

Metrology Science of measurement and its application

Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in France, when a length standard taken from a natural source was proposed. This led to the creation of the decimal-based metric system in 1795, establishing a set of standards for other types of measurements. Several other countries adopted the metric system between 1795 and 1875; to ensure conformity between the countries, the Bureau International des Poids et Mesures (BIPM) was established by the Metre Convention. This has evolved into the International System of Units (SI) as a result of a resolution at the 11th Conference Generale des Poids et Mesures (CGPM) in 1960.

Troy weight System of units of mass

Troy weight is a system of units of mass that originated in 15th-century England, and is primarily used in the precious metals industry. The Troy weights are the grain, the pennyweight, the troy ounce, and the troy pound. The troy grain is equal to the grain-unit of the avoirdupois system, the troy ounce is heavier than the avoirdupois ounce, yet the troy pound is lighter than the avoirdupois pound.

Centi- is a unit prefix in the metric system denoting a factor of one hundredth. Proposed in 1793 and adopted in 1795, the prefix comes from the Latin centum, meaning "hundred". Since 1960, the prefix is part of the International System of Units (SI). It is mainly used in combination with metre to form centimetre, a common unit of length.

Milli- is a unit prefix in the metric system denoting a factor of one thousandth (10−3). Proposed in 1793 and adopted in 1795, the prefix comes from the Latin mille, meaning "one thousand". Since 1960, the prefix is part of the International System of Units (SI).

Deci- is a decimal unit prefix in the metric system denoting a factor of one tenth. Proposed in 1793 and adopted in 1795, the prefix comes from the Latin decimus, meaning "tenth". Since 1960, the prefix is part of the International System of Units (SI). Its most frequent use, however, is in a non-SI unit, the decibel, used to measure sound intensity and many other ratios.

Quintus Remmius Palaemon or Quintus Rhemnius Fannius Palaemon was a Roman grammarian and a native of Vicentia. He lived during the reigns of Emperors Tiberius and Claudius.

Mesures usuelles were a French system of measurement introduced by Napoleon I in 1812 to act as compromise between the metric system and traditional measurements. The system was restricted to use in the retail industry and continued in use until 1840, when the laws of measurement from the 1795 and 1799 were reinstituted.

Units of measurement in France

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Grave (unit)

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Hectare Metric unit of area

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The history of the metric system began during the Age of Enlightenment with measures of length and weight derived from nature, along with their decimal multiples and fractions. The system became the standard of France and Europe within half a century. Other dimensions with unity ratios were added, and the system went on to be adopted across the world.

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Outline of the metric system Overview of and topical guide to the metric system

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  1. "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.
  2. "Décret relatif aux poids et aux mesures" (in French). 1795. Archived from the original on 25 February 2013.
  3. 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)
  4. Decision CIPM/105-13 (October 2016). The day is the 144th anniversary of the Metre Convention.
  5. National Institute of Standards and Technology (October 2011). Butcher, Tina; Cook, Steve; Crown, Linda et al. eds. "Appendix C – General Tables of Units of Measurement" Archived 2016-06-17 at the Wayback Machine (PDF). Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices Archived 2016-08-23 at the Wayback Machine . NIST Handbook. 44 (2012 ed.). Washington, D.C.: U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology. ISSN 0271-4027. OCLC OCLC   58927093. Retrieved 30 June 2012.
  6. "Décret relatif aux poids et aux mesures du 18 germinal an 3 (7 avril 1795)" [Decree of 18 Germinal, year III (April 7, 1795) regarding weights and measures]. Grandes lois de la République (in French). Digithèque de matériaux juridiques et politiques, Université de Perpignan. Archived from the original on 10 May 2013. Retrieved 3 November 2011.
  7. Convention nationale, décret du 1er août 1793, ed. Duvergier, Collection complète des lois, décrets, ordonnances, règlemens avis du Conseil d'état, publiée sur les éditions officielles du Louvre, vol. 6 (2nd ed. 1834), p. 70 Archived 2015-04-02 at the Wayback Machine . The metre (mètre) on which this definition depends was itself defined as the ten-millionth part of a quarter of Earth's meridian, given in traditional units as 3 pieds , 11.44 lignes (a ligne being the 12th part of an pouce (inch), or the 144th part of a pied.
  8. Charlton T. Lewis, Charles Short, A Latin Dictionary s.v. "gramma" Archived 2015-07-17 at the Wayback Machine , 1879
  9. Knorr, Wilbur R. (1996). "Carmen de ponderibus et mensuris". In Hornblower, Simon; Spawforth, Antony (eds.). The Oxford Classical Dictionary (3rd ed.). Oxford: Oxford University Press. p.  292. ISBN   019866172X.
  10. Henry George Liddell. Robert Scott. A Greek-English Lexicon (revised and augmented edition, Oxford, 1940) s.v. γράμμα Archived 2015-07-17 at the Wayback Machine , citing the 10th-century work Geoponica and a 4th-century papyrus edited in L. Mitteis, Griechische Urkunden der Papyrussammlung zu Leipzig, vol. i (1906), 62 ii 27.
  11. Pat Chapman (2007). India Food and Cooking: The Ultimate Book on Indian Cuisine. London: New Holland Publishers (UK) Ltd. p. 64. ISBN   978-1845376192 . Retrieved 20 November 2014. Most of the world uses the metric system to weigh and measure. This book puts metric first, followed by imperial because the US uses it (with slight modifications which need not concern us).
  12. Gisslen, Wayne (2010). Professional Cooking, College Version. New York: Wiley. p. 107. ISBN   0-470-19752-8 . Retrieved 20 April 2011. The system of measurement used in the United States is complicated. Even when people have used the system all their lives, they still sometimes have trouble remembering things like how many fluid ounces are in a quart or how many feet are in a mile. ... The United States is the only major country that uses almost exclusively the complex system of measurement we have just described.
  13. "System of Measurement Units - Engineering and Technology History Wiki". Archived from the original on 29 April 2018. Retrieved 29 April 2018.
  14. "Circulating Coin Designs". Japan Mint. Archived from the original on 18 September 2009. Retrieved 7 March 2010.