SI Multiples
Because SI prefixes may not be concatenated (serially linked) within the name or symbol for a unit of measure, SI prefixes are used with the gram, not the kilogram, which already has a prefix as part of its name. For instance, one-millionth of a kilogram is 1 mg (one milligram), not 1 µkg (one microkilogram).
| Submultiples | Multiples | |||||
|---|---|---|---|---|---|---|
| Value | Symbol | Name | Value | Symbol | Name | |
| 10−1 g | dg | decigram | 101 g | dag | decagram | |
| 10−2 g | cg | centigram | 102 g | hg | hectogram | |
| 10−3 g | mg | milligram | 103 g | kg | kilogram | |
| 10−6 g | µg | microgram (mcg) | 106 g | Mg | megagram (tonne) | |
| 10−9 g | ng | nanogram | 109 g | Gg | gigagram | |
| 10−12 g | pg | picogram | 1012 g | Tg | teragram | |
| 10−15 g | fg | femtogram | 1015 g | Pg | petagram | |
| 10−18 g | ag | attogram | 1018 g | Eg | exagram | |
| 10−21 g | zg | zeptogram | 1021 g | Zg | zettagram | |
| 10−24 g | yg | yoctogram | 1024 g | Yg | yottagram | |
| Common prefixes are in bold face. | ||||||
- When the Greek lowercase “µ” (mu) in the symbol of microgram is typographically unavailable, it is occasionally—although not properly—replaced by Latin lowercase “u”.
- The microgram is often abbreviated “mcg”, particularly in pharmaceutical and nutritional supplement labeling, to avoid confusion since the “µ” prefix is not well recognized outside of technical disciplines. Note however, that the abbreviation “mcg”, is also the symbol for an obsolete CGS unit of measure known as the “millicentigram”, which is equal to 10 µg.
- The decagram (dag) is in Central Europe often abbreviated “dkg” (from local languages spelling “dekagram”) and is used for usual quantities of food (mostly cheese and meat).
- The unit name “megagram” is rarely used, and even then, typically only in technical fields in contexts where especially rigorous consistency with the units of measure is desired. For most purposes, the unit “tonne” is instead used. The tonne and its symbol, t, were adopted by the CIPM in 1879. It is a non-SI unit accepted by the BIPM for use with the SI. According to the BIPM, “In English speaking countries this unit is usually called ‘metric ton’.” Note also that the unit name “megatonne” or “megaton” (Mt) is often used in general-interest literature on greenhouse gas emissions whereas the equivalent value in scientific papers on the subject is often the “teragram” (Tg).
Read more about this topic: Kilogram
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