notation to specify resistor and capacitor values
The RKM code, [ 1 ] besides referred to as “ letter and numeral code for electric resistance and capacitance values and tolerances ”, [ 1 ] “ letter and digit code for resistance and capacitor values and tolerances ”, [ 2 ] [ 3 ] or “ roentgen note ” [ citation needed ], is a notation to specify resistor and capacitor values defined in the international criterion IEC 60062 ( once IEC 62 ) since 1952. It is besides adopted by assorted other standards including DIN 40825 ( 1973 ), BS 1852 ( 1974 ), IS 8186 ( 1976 ) and EN 60062 ( 1993 ). The significantly updated IEC 60062:2016 comprises the most recent turn of the standard. [ 1 ]


primitively meant besides 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 model in bills of material and in silk screens ). This method avoids overlooking the decimal centrifuge, which may not be rendered faithfully on components or when duplicating documents. The standards besides define a color code for fixed resistors.

partially value code.

Examples of resistance values[4]
R47 0.47 ohm
4R7 4.7 ohm
470R 470 ohm
4K7 4.7 kilohm
47K 47 kilohm
47K3 47.3 kilohm
470K 470 kilohm
4M7 4.7 megohm

For brevity, the note omits to always specify the unit ( ohm or farad ) explicitly and alternatively relies on implicit cognition raised from the custom of specific letters either only for resistors or for capacitors, [ nota bene 1 ] the case used ( capital letters are typically used for resistors, small letter letters for capacitors ), [ niobium 2 ] a region ‘s appearance, and the context. The notation besides avoids using a decimal centrifuge and replaces it by a letter associated with the prefix symbol for the especial measure. This is not only for brevity ( for example when printed on the depart or PCB ), but besides to circumvent the problem that decimal separators tend to “ disappear ” when photocopying printed circuit diagrams. The code letters are loosely related to the correspond SI prefix, but there are several exceptions, where the capitalization differs or option letters are used. For example, 8K2 indicates a resistor value of 8.2 kΩ. Additional nothing imply tighter allowance, for exemplar 15M0. When the value can be expressed without the motivation for a prefix, an “ gas constant ” is used alternatively of the decimal centrifuge. For exercise, 1R2 indicates 1.2 Ω, and 18R indicates 18 Ω .
For resistances, the standard dictates the practice of the capital letters L ( for 10−3 ), R ( for 100 = 1 ), K ( for 103 ), M ( for 106 ), and G ( for 109 ) to be used rather of the decimal point. The use of the letter R rather of the SI unit symbol Ω for ohm 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 ) and consequently is sometimes impossible to reproduce, in finical in some CAD/CAM environments. The letter R was chosen because visually it loosely resembles the Ω glyph, and besides because it works nicely as a mnemonic for r esistance in many languages. The letters G and T were n’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 equate SI prefixes. The initiation of the letter L in more holocene issues of the standard ( alternatively of an SI prefix m for milli ) is absolve to maintain the predominate of alone using uppercase letters for resistances ( the differently resulting M was already in use for mega ). like, the standard prescribes the come lowercase letters for capacitances to be used alternatively of the decimal point : p ( for 10−12 ), n ( for 10−9 ), µ ( for 10−6 ), m ( for 10−3 ), but capital F ( for 100 = 1 ) for farad. The letters p and n were n’t separate of the first base topic of the criterion, but were added after the adoption of the corresponding SI prefixes.

In cases where the greek letter µ is not available, the criterion allows it to be replaced by u ( or U, when entirely capital letters are available ). This use of u alternatively of µ is besides in line with ISO 2955 ( 1974, [ 6 ] 1983 [ 7 ] ), DIN 66030 ( Vornorm 1973 ; [ 8 ] 1980, [ 9 ] [ 10 ] 2002 [ 11 ] ) and BS 6430 ( 1983 ), which allow the prefix μ to be substituted by the letter u ( or U ) in circumstances in which lone the Latin rudiment is available .

permissiveness code.

Letter code for resistance and capacitor tolerances :

Code letter Tolerance
Resistance Capacitance Relative Absolute
Symmetrical Asymmetrical C <10 pF only
A A variable (±0.05%) variable variable
B B ±0.1% N/A
C C ±0.25% N/A ±0.25 pF
D D ±0.5% N/A ±0.5 pF
E ±0.005% N/A N/A
F F ±1.0% N/A ±1.0 pF
G G ±2.0% N/A ±2.0 pF
H H ±3.0% N/A N/A
J J ±5.0% N/A N/A
K K ±10% N/A N/A
L ±0.01% N/A N/A
M M ±20% N/A N/A
N ±30% N/A N/A
P ±0.02% N/A N/A
Q N/A −10/+30% N/A
S N/A −20/+50% N/A
T N/A −10/+50% N/A
W ±0.05% N/A N/A
Z N/A −20/+80% N/A

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 context following the American War Standard ( AWS ) and articulation Army-Navy Specifications ( JAN ) since the mid-1940s. [ 12 ]

Temperature coefficient code.

Letter codes for resistor temperature coefficients :

Code letter ppm/K
K 1
M 5
P 15
Q 25
R 50
S 100
U 250
Z other

example : V8 = August 2007 ( or August 1987 ) Some manufacturers besides used the production date code as a stand-alone code to indicate the product date of desegregate circuits. [ 16 ]

alike codes.

A exchangeable not standardize notation using the unit symbol rather of a decimal centrifuge is sometimes used to indicate voltages ( 3V3 for 3.3 V, or 1V8 for 1.8 V ) in context where a decimal centrifuge would be inappropriate ( e.g. in signal names or file names ) .

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)[17]
  • 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)[2]
  • IEC 60062:2016 (sixth edition, 2016-07-12)[1]
  • IEC 60062:2016/COR1:2016 (corrected sixth edition, 2016-12-05)
  • EN 60062:1993
  • EN 60062:1994 (1994-10)
  • EN 60062:2005
  • EN 60062:2016
  • BS 1852:1975[18] (related to IEC 60062:1974)
  • BS EN 60062:1994[19]
  • BS EN 60062:2005[20]
  • BS EN 60062:2016[21]
  • 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[15] (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[22]
  • IS 8186-1976[23] (related to IEC 62:1974)
  • JIS C 5062
  • TGL 31667[24]

See besides.


  1. a b c The letter M was an exception to the rule that all unlike letters are supposed to be used for resistances and capacitances. nowadays, a small letter letter m should be used for capacitances whenever possible to avoid confusion .
  2. a b c d e In old issues of the IEC 60062 standard, capital latin letters were not entirely used for resistances, but besides for capacitor values, whereas newer issues specifically use small letter letters for capacitors ( except for the particular case of F ) .
  3. ^E instead of R is not standardized in IEC 60062, but nevertheless sometimes seen in practice. It stems from the fact, that R is used in symbolic names for resistors as well, and it is also used in a similar fashion but with incompatible meaning in other part marking codes. It may therefore cause confusion in some contexts. Visually, the letter E loosely resembles a small Greek letter ω for 56 Ω. However, the letter E is conflictive with the similar looking but incompatible The use of the Latin letterinstead ofis not standardized in IEC 60062, but however sometimes seen in commit. It stems from the fact, thatis used in symbolic names for resistors american samoa well, and it is besides used in a like manner but with incompatible mean in other function marking codes. It may therefore cause confusion in some context. visually, the letterloosely resembles a modest greek letter omega ( ω ) turned sideways. Historically ( f.e. in pre- WWII documents ), before ohms were denoted using the capital Greek omega ( Ω ), a belittled omega ( ω ) was sometimes used for this purpose adenine well, as in 56for 56 Ω. however, the letteris conflictive with the alike looking but incompatible E notation in technology, and it may therefore induce considerable confusion as well .
  4. ^K only, however, a lowercase k is often seen in k. The IEC 60062 criterion prescribes the use of an uppercase Latin letteronly, however, a lowercaseis often seen in schematics and bills of materials credibly because the match SI prefix is defined as a small letter
  5. ^ In order to reduce the risk for read errors, the letters G ( 6 ), I ( J, 1 ), O ( 0, Q, D ), Q ( O, D, 0 ), Y, Z ( 2 ) are not used as their glyph look similar to other letters and digits.
  6. ^ due to the ambiguity of many month initials ( A, J, M ) the code for the most part uses digits. Since letter O is well confused with finger 0, the code is arranged so that the letter O is used for October, the one-tenth calendar month, preferably than for January .


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