Guidance is provided to aid general public use of the metric system. Webster’s pronunciation guidance reflects contemporary American English. For example, the prefix deka is used (American English spelling) but not deca (British English). It’s important to note that spelling in NIST publications are made in accordance with the United States Government Printing Office Style Manual, which follows American English writing practices found in Webster's Third New International Dictionary. The names of such multiples and submultiples are formed by attaching SI prefix names to the name "gram." Example: 1 mg, NOT 1 μkg (1 microkilogram). Thus, because compound prefixes are unacceptable, symbols for decimal multiples and submultiples of the unit of mass are formed by attaching SI prefix symbols to g (gram). For historical reasons, the name "kilogram" for the SI base unit of mass contains the name "kilo," the SI prefix for 10 3. SI prefixes for submultiples (smaller quantities or sub units) are formatted with all lowercase symbols while prefixes for multiples (larger quantities or whole units) use uppercase symbols with the exception of three: kilo (k), hecto (h) and deka (da). Two forming submultiples: ronto and quecto.Ĭapitalization. Two for forming multiples: ronna and quetta. Two for forming submultiples: zepto and yocto.įour prefixes were added. Two for forming multiples: zetta and yotta.
Two prefixes for forming multiples were added: peta and exa.įour prefixes were added. This created an imbalanced situation, where there were more prefixes for small quantities. Two prefixes for forming submultiples were added: femto and atto. Three for forming submultiples: micro, nano, and pico. Three for forming multiples: mega, giga, and tera. Two prefixes were made obsolete: myria and myrio. The first General Conference on Weights and Measures (CGPM) approves the 8 prefixes for use. This chronological summary highlights these developments.Įight original SI prefixes were officially adopted: deca, hecto, kilo, myria, deci, centi, milli, and myrio, derived from Greek and Latin numbers. Initially, all prefixes were represented by lowercase symbols. Prefix Progress. Since the first eight prefixes were adopted by the CGPM in 1889, there have been five subsequent prefix expansions.
* SI base or derived units with special names may be used The convention of writing a zero before the decimal point is used to ensure that the quantity is appropriately interpreted. Use a leading zero for numbers less than one. Note that the recommended decimal sign or marker for use in the United States is the dot on the line, which is used to separate whole numbers from parts.
The simplified table below shows common metric prefixes and the relationship with their place values. The following table of 24 SI prefixes ranging from 10 30 to 10 −30 are currently recognized for use. In certain cases, particularly in scientific usage, it becomes convenient to provide for multiples larger than 1000 and for subdivisions smaller than one-thousandth. In the SI, designations of multiples and subdivision of any unit may be arrived at by combining with the name of the unit the prefixes deka, hecto, and kilo meaning, respectively, 10, 100, and 1000, and deci, centi, and milli, meaning, respectively, one-tenth, one-hundredth, and one-thousandth. The conversion factor that does this is the one on the right. Values of quantities are expressed using Arabic symbols for numbers paired with a unit symbol, often with a prefix symbol that modifies unit magnitude. We use the conversion factor that will cancel out the original unit, liters, and introduce the unit we are converting to, which is milliliters.
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