The RKM code, also referred to as "letter and numeral code for resistance and capacitance values and tolerances", "letter and digit code for resistance and capacitance values and tolerances", or informally as "R notation" is a notation to specify resistor and capacitor values defined in the international standard
IEC The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
 60062 (formerly IEC 62) since 1952. It is also adopted by various other standards including DIN 40825 (1973), BS 1852 (1975), IS 8186 (1976) and EN 60062 (1993). The updated IEC 60062:2016, amended in 2019, comprises the most recent release of the standard.


Originally meant also as part marking code, this shorthand notation is widely used in electrical engineering to denote the values of resistors and capacitors in circuit diagrams and in the production of electronic circuits (for example in bills of material and in
silk screen Screen printing is a printing technique where a mesh is used to transfer ink (or dye) onto a Substrate (printing), substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen t ...
s). This method avoids overlooking the decimal separator, which may not be rendered reliably on components or when duplicating documents. The standards also define a ''
color code for fixed resistors An electronic color code or electronic colour code (see spelling differences) is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, diodes and others. A separate code, the ...

Part value code

For brevity, the notation omits to always specify the unit (
ohm Ohm (symbol Ω) is a unit of electrical resistance named after Georg Ohm. Ohm or OHM may also refer to: People * Georg Ohm (1789–1854), German physicist and namesake of the term ''ohm'' * Germán Ohm (born 1936), Mexican boxer * Jörg Ohm (bor ...
or farad) explicitly and instead relies on implicit knowledge raised from the usage of specific letters either only for resistors or for capacitors, the case used (uppercase letters are typically used for resistors, lowercase letters for capacitors), a part's appearance, and the context. The notation also avoids using a decimal separator and replaces it by a letter associated with the prefix symbol for the particular value. This is not only for brevity (for example when printed on the part or PCB), but also to circumvent the problem that decimal separators tend to "disappear" when
photocopy A photocopier (also called copier or copy machine, and formerly Xerox machine, the generic trademark) is a machine that makes copies of documents and other visual images onto paper or plastic film quickly and cheaply. Most modern photocopier ...
ing printed circuit diagrams. The code letters are loosely related to the corresponding SI prefix, but there are several exceptions, where the capitalization differs or alternative letters are used. For example, 8K2 indicates a resistor value of 8.2 kΩ. Additional zeros imply tighter tolerance, for example 15M0. When the value can be expressed without the need for a prefix, an "R" is used instead of the decimal separator. For example, 1R2 indicates 1.2 Ω, and 18R indicates 18 Ω. For ''resistances'', the standard dictates the use of the uppercase letters L (for 10−3), R (for 100 = 1), K (for 103), M (for 106), and G (for 109) to be used instead of the decimal point. The usage of the letter R instead of the SI unit symbol Ω for ohms stems from the fact that the Greek letter Ω is absent from most older character encodings (though it is present in the now-ubiquitous
Unicode Unicode, formally The Unicode Standard,The formal version reference is is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, ...
) and therefore is sometimes impossible to reproduce, in particular in some CAD/CAM environments. The letter R was chosen because visually it loosely resembles the Ω glyph, and also because it works nicely as a mnemonic for ''r''esistance in many languages. The letters G and T weren't part of the first issue of the standard, which pre-dates the introduction of the SI system (hence the name "RKM code"), but were added after the adoption of the corresponding SI prefixes. The introduction of the letter L in more recent issues of the standard (instead of an SI prefix m for milli) is justified to maintain the rule of only using uppercase letters for resistances (the otherwise resulting M was already in use for mega). Similar, the standard prescribes the following lowercase letters for ''capacitances'' to be used instead of the decimal point: p (for 10−12), n (for 10−9), µ (for 10−6), m (for 10−3), but uppercase F (for 100 = 1) for farad. The letters p and n weren't part of the first issue of the standard, but were added after the adoption of the corresponding SI prefixes. In cases where the Greek letter µ is not available, the standard allows it to be replaced by u (or U, when only uppercase letters are available). This usage of u instead of µ is also in line with ISO 2955 (1974, 1983), DIN 66030 (Vornorm 1973; 1980, 2002), BS 6430 (1983) and
Health Level 7 Health Level Seven or HL7 refers to a set of international standards for transfer of clinical and administrative data between software applications used by various healthcare providers. These standards focus on the application layer, which is "la ...
(HL7), which allow the prefix μ to be substituted by the letter u (or U) in circumstances in which only the
Latin alphabet The Latin alphabet or Roman alphabet is the collection of letters originally used by the ancient Romans to write the Latin language. Largely unaltered with the exception of extensions (such as diacritics), it used to write English and the ...
is available.

Similar codes

Though non-standardized some manufacturers use the RKM code also to mark inductors with "R" marking the decimal point in microhenry (e.g. 4R7 for 4.7 μH). A similar not standardized notation using the unit symbol instead of a decimal separator is sometimes used to indicate voltages (3V3 for 3.3 V, or 1V8 for 1.8 V) in contexts where a decimal separator would be inappropriate (e.g. in signal names or
file name A filename or file name is a name used to uniquely identify a computer file in a directory structure. Different file systems impose different restrictions on filename lengths. A filename may (depending on the file system) include: * name &ndas ...

Tolerance code

Letter code for resistance and capacitance tolerances: Before the introduction of the RKM code, some of the letters for symmetrical tolerances (viz. G, J, K, M) were already used in US military contexts following the
American War Standard American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the " United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, p ...
(AWS) and
Joint Army-Navy The Joint Electronics Type Designation System (JETDS), which was previously known as the Joint Army-Navy Nomenclature System (AN System. JAN) and the Joint Communications-Electronics Nomenclature System, is a method developed by the U.S. War Depar ...
Specifications (JAN) since the mid-1940s.

Temperature coefficient code

Letter codes for the temperature coefficient of resistance (TCR):

Production date codes

Twenty-year cycle code

* First character: Year of production in twenty-year cycle ** A = 2030, 2010, 1990, 1970 ** B = 2031, 2011, 1991, 1971 ** C = 2032, 2012, 1992, 1972 ** D = 2033, 2013, 1993, 1973 ** E = 2034, 2014, 1994, 1974 ** F = 2035, 2015, 1995, 1975 ** H = 2036, 2016, 1996, 1976 ** J = 2037, 2017, 1997, 1977 ** K = 2038, 2018, 1998, 1978 ** L = 2039, 2019, 1999, 1979 ** M = 2020, 2000, 1980 ** N = 2021, 2001, 1981 ** P = 2022, 2002, 1982 ** R = 2023, 2003, 1983 ** S = 2024, 2004, 1984 ** T = 2025, 2005, 1985 ** U = 2026, 2006, 1986 ** V = 2027, 2007, 1987 ** W = 2028, 2008, 1988 ** X = 2029, 2009, 1989 * Second character: Month of production ** 1 to 9 = January to September ** O = October ** N = November ** D = December Example: J8 = August 2017 (or August 1997) Some manufacturers also used the production date code as a stand-alone code to indicate the production date of integrated circuits. Some manufacturers specify a three-character date code with a two-digit week number following the year letter. IEC 60062 also specifies a four-character year/week code.

Ten-year cycle code

* First character: Year of production in ten-year cycle ** 0 = 2020 ** 1 = 2021 ** 2 = 2022, 2012 ** 3 = 2023, 2013 ** 4 = 2024, 2014 ** 5 = 2025, 2015 ** 6 = 2026, 2016 ** 7 = 2017 ** 8 = 2018 ** 9 = 2019 * Second character: Month of production ** 1 to 9 = January to September ** X = October ** Y = November ** Z = December Example: 78 = August 2017 IEC 60062 also specifies a four-character year/week code.

Four-year cycle code

IEC 60062 also specifies a single-character four-year cycle year/month code.

Marking codes for E series preferred values

Three-character resistor marking code

For resistances following the ( E48 or)
E96 series The E series is a system of preferred numbers (also called preferred values) derived for use in electronic components. It consists of the E3, E6, E12, E24, E48, E96 and E192 series, where the number after the 'E' designates the quantity of ...
of preferred values, the former EIA-96 as well as IEC 60062:2016 define a '' special three-character marking code for resistors'' to be used on small parts. The code consists of two digits denoting one of the "positions" in the series of E96 values followed by a letter indicating the multiplier.

Two-character capacitor marking code

For capacitances following the ( E3, E6, E12 or) E24 series of preferred values, the former ANSI/EIA-198-D:1991, ANSI/EIA-198-1-E:1998 and ANSI/EIA-198-1-F:2002 as well as the amendment IEC 60062:2016/AMD1:2019 to IEC 60062 define a '' special two-character marking code for capacitors'' for very small parts which leave no room to print any longer codes onto them. The code consists of an uppercase letter denoting the two significant digits of the value followed by a digit indicating the multiplier. The EIA standard also defines a number of lowercase letters to specify a number of values not found in E24.

Corresponding standards

* IEC 62:1952 (aka IEC 60062:1952), first edition, 1952-01-01 * IEC 62:1968 (aka IEC 60062:1968), second edition, 1968-01-01 * IEC 62:1968/AMD1:1968 (aka IEC 60062:1968/AMD1:1968), amended second edition, 1968-12-31 * IEC 62:1974 (aka IEC 60062:1974) * IEC 62:1974/AMD1:1988 (aka IEC 60062:1974/AMD1:1988), amended third edition, 1988-04-30 * IEC 62:1974/AMD2:1989 (aka IEC 60062:1974/AMD2:1989), amended third edition, 1989-01-01 * IEC 62:1992 (aka IEC 60062:1992), fourth edition, 1992-03-15 * IEC 62:1992/AMD1:1995 (aka IEC 60062:1992/AMD1:1995), amended fourth edition, 1995-06-19 * IEC 60062:2004 (fifth edition, 2004-11-08) * IEC 60062:2016 (sixth edition, 2016-07-12) * IEC 60062:2016/COR1:2016 (corrected sixth edition, 2016-12-05) * IEC 60062:2016/AMD1:2019 (amendment 1, 2019-08-20) * IEC 60062:2016+AMD1:2019 CSV (consolidated version 6.1, 2019-08-20) * EN 60062:1993 * EN 60062:1994 (1994-10) * EN 60062:2005 * EN 60062:2016 * EN 60062:2016/AC:2016-12 (corrected edition) * EN 60062:2016/A1:2019 (amendment 1) * BS 1852:1975 (related to IEC 60062:1974) * BS EN 60062:1994 * BS EN 60062:2005 * BS EN 60062:2016 * DIN 40825:1973-04 (capacitor/resistor value code), DIN 41314:1975-12 (date code) * DIN IEC 62:1985-12 (aka DIN IEC 60062:1985-12) * DIN IEC 62:1989-10 (aka DIN IEC 60062:1989-10) * DIN IEC 62:1990-11 (aka DIN IEC 60062:1990-11) * DIN IEC 62:1993-03 (aka DIN IEC 60062:1993-03) * DIN EN 60062:1997-09 * DIN EN 60062:2001-11 * DIN EN 60062:2005-11 * ČSN EN 60062 * DS/EN 60062 * EVS-EN 60062 * (GOST) ГОСТ IEC 60062-2014 (related to IEC 60062-2004) * ILNAS-EN 60062 * I.S. EN 60062 * NEN EN IEC 60062 * NF EN 60062 * ÖVE/ÖNORM EN 60062 * PN-EN 60062 * prМКС EN 60062 * SN EN 60062 * TS 2932 EN 60062 * UNE-EN 60062 * BIS IS 4114-1967 * IS 8186-1976 (related to IEC 62:1974) * JIS C 5062 * TGL 31667

See also

Electronic color code An electronic color code or electronic colour code (see spelling differences) is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, diodes and others. A separate code, the ...
* SI prefix *
Metric prefix A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The pr ...
Engineering notation Engineering notation or engineering form (also technical notation) is a version of scientific notation in which the exponent of ten must be divisible by three (i.e., they are powers of a thousand, but written as, for example, 106 instead of 1000 ...
* E notation *
Cifrão The dollar sign, also known as peso sign, is a symbol consisting of a capital " S" crossed with one or two vertical strokes ($ or ), used to indicate the unit of various currencies around the world, including most currencies denominated "pe ...
(a similar scheme for a currency) *
Fermata A fermata (; "from ''fermare'', to stay, or stop"; also known as a hold, pause, colloquially a birdseye or cyclops eye, or as a grand pause when placed on a note or a rest) is a symbol of musical notation indicating that the note should be ...
(a remotely similar musical notation)



{{List of IEC standards Standards