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| gram | |
|---|---|
| Name | Gram |
| Quantity | Mass |
| Units1 | SI base units |
| Units1 expr | kg·m²/s²·s²/kg? |
gram The gram is a unit of mass used widely in science, industry, and daily life. It is part of the metric system and relates directly to the kilogram, the International System of Units standard adopted by many countries and international bodies. The unit appears in metrology, chemistry, pharmaceuticals, nutrition, and commerce, and is referenced in standards set by organizations such as the International Bureau of Weights and Measures, the European Commission, and national metrology institutes.
The gram is defined as one thousandth of the kilogram, which is the SI unit of mass; its symbol is g. This definition ties the unit to the kilogram as realized by international prototypes and, since 2019, to the fixed numerical value of the Planck constant as adopted by the General Conference on Weights and Measures. The symbol g is used in technical documents published by bodies like the International Organization for Standardization and standards committees within the International Electrotechnical Commission, the National Institute of Standards and Technology, and the Bureau International des Poids et Mesures.
The genesis of the gram traces to late 18th-century France during reform efforts associated with the French Revolution, when commissions including figures from the Academy of Sciences proposed decimal-based units; contemporaries included scientists working with the meridian-based metre definition adopted by the National Assembly and figures connected to institutions like the École Polytechnique and the Conservatoire des Arts et Métiers. Subsequent international conferences such as the Metre Convention led to the creation of the International Bureau of Weights and Measures and agreements finalized in works circulated among national standards agencies in London, Berlin, Vienna, and Washington. Over the 19th and 20th centuries, national laboratories—examples being the Physikalisch-Technische Bundesanstalt, the National Research Council of Canada, and the Laboratoire national de métrologie et d'essais—refined prototypes, eventually culminating in the 2019 SI redefinition advocated by committees at the General Conference on Weights and Measures and endorsed by member states.
Metrology for the gram has been overseen through successive physical prototypes, calibration hierarchies, and traceability schemes administered by organizations such as the International Committee for Weights and Measures and regional bodies like the European Committee for Standardization. Calibration chains link national prototypes maintained by institutes such as the National Physical Laboratory, the National Institute of Metrology (China), and the Instituto Nacional de Tecnología Industrial to laboratory standards used in research centers including CERN, NASA, and the Max Planck Society. Quality systems in laboratories follow guidelines from the International Organization for Standardization and accreditation by bodies aligned with the International Laboratory Accreditation Cooperation to ensure measurements in grams are comparable across commerce, healthcare, and research.
The gram is ubiquitous: chemists in universities like the University of Cambridge, MIT, and the University of Tokyo report reagent masses in grams; pharmacists in hospitals such as Mayo Clinic and Karolinska University Hospital compound doses specified in milligrams and grams; food industry standards from the Food and Agriculture Organization and the World Health Organization list nutritional values per 100 grams. Retail trade in supermarkets like Carrefour, Tesco, and Walmart uses gram-based labeling alongside regional units; postal services including Deutsche Post and United States Postal Service calculate postage for small parcels in grams. In laboratories at institutions such as Lawrence Berkeley National Laboratory and the Max Planck Institute, precision balances resolve masses to sub-milligram levels for experiments in materials science, nanotechnology, and pharmacology.
Common derived and related units include the milligram, kilogram, tonne, and ounce; conversions are standardized in technical tables issued by bodies like the International Bureau of Weights and Measures and national standards agencies. Practical conversion examples appear in manufacturing standards from ASTM International and ISO: 1 kilogram equals 1000 grams, 1 gram equals 1000 milligrams, and approximate non-SI equivalents are used in contexts involving the United States customary units as tabulated by the National Institute of Standards and Technology and other metrology centers. Unit conversion calculators and software maintained by organizations such as the European Central Bank for trade data, the World Bank for development indicators, and research libraries at institutions like Harvard and Oxford routinely include gram-based conversions.
The term originates from French and Neo-Latin roots developed during metric reform efforts and is related to linguistic formations used by scholars affiliated with the Académie Française and universities across Europe. Adoption of the term in legal and technical texts appears in statutes and regulations promulgated by parliaments and ministries in countries from France and Germany to Japan and Brazil, and in international treaties and agreements overseen by the League of Nations predecessors and later by the United Nations. Usage in style guides and lexicons produced by publishers such as Oxford University Press, Cambridge University Press, and Elsevier standardizes the symbol and abbreviation in scientific publishing and technical documentation.