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{{Short description|Color code to indicate values of electronic components}}
{{Use dmy dates|date=January 2020|cs1-dates=y}}
{{Use list-defined references|date=December 2021}}
[[Image:2.26 kilo-ohm precision resistor.jpg|thumb|upright|A {{val|2.26|ul=kΩ}}, 1%-precision resistor with 5 color bands ([[E96 series]]), from top, 2-2-6-1-1; the last two brown bands indicate the multiplier (×10) and the tolerance (1%).]]
An '''electronic color code''' or '''electronic colour code''' (see [[American and British English spelling differences#-our, -or|spelling differences]]) is used to indicate the values or ratings of electronic components, usually for [[resistor]]s, but also for [[capacitor]]s, [[inductor]]s, [[diode]]s and others. A separate code, the [[25-pair color code]], is used to identify wires in some [[telecommunications]] cables. Different codes are used for wire leads on devices such as transformers or in building wiring.

==History==
{{anchor|RMA|RTMA|RETMA|EIA|IEC}}
[[File:ResistorColorCodeGuide.jpg|thumb|[[Radio Manufacturers Association|RMA]] resistor color code guide, ca. 1945–1950]]
Before industry standards were established, each manufacturer used its own unique system for color coding or marking their components.

In the 1920s,{{Citation needed|date=November 2019|reason=Please help nail down the exact year of the RMA resistor color specification. It's in the range of 1924 to 1930.}} the '''RMA resistor color code''' was developed by the [[Radio Manufacturers Association]] (RMA) as a fixed resistor coloring code marking.  In 1930, the first [[Radio receiver|radio]]s with RMA color-coded resistors were built.<ref name="ARH_1932_1"/><ref name="ARH_1932_2"/> Over many decades, as the organization name changed (RMA, RTMA, RETMA, [[Electronic Industries Alliance|EIA]])<ref name="JEDEC_EIA"/> so was the name of the code. Though known most recently as '''EIA color code''', the four name variations are found in books, magazines, catalogs, and other documents over more than {{Years ago|1930}} years.

In 1952, it was standardized in [[IEC 62:1952]] by the [[International Electrotechnical Commission]] (IEC) and since 1963 also published as '''EIA RS-279'''.<ref name="EIA_RS-279"/> Originally only meant to be used for fixed resistors, the color code was extended to also cover capacitors with [[IEC 62:1968]]. The code was adopted by many national standards like [[DIN 40825]] (1973), [[BS 1852]] (1974) and [[IS 8186]] (1976). The current international standard defining marking codes for resistors and capacitors is [[IEC 60062:2016]].<ref name="IEC_60062_2016"/> In addition to the color code, these standards define a letter and digit code named [[RKM code]] for resistors and capacitors.

Color bands were used because they were easily and cheaply printed on tiny components. However, there were drawbacks, especially for [[Color blindness|color blind]] people. Overheating of a component or dirt accumulation may make it impossible to distinguish brown from red or orange. Advances in printing technology have now made printed numbers more practical on small components. The values of components in [[surface mount]] packages are marked with printed alphanumeric codes instead of a color code.

==Resistors==
{{anchor|Resistor code}}
[[Image:Preferred values 05 Pengo.svg|thumb|One decade of the [[E12 series]] (there are twelve preferred values per decade of values) shown with their electronic color codes on [[resistor]]s]]
[[Image:0-ohm.jpg|thumb|A [[Zero-ohm link|0&nbsp;Ω resistor]] (zero ohm), marked with a single black band]]

===Color band system===
To distinguish left from right there is a gap between the C and D bands:
[[Image:Resistor bands.svg|A diagram of a resistor, with four color bands A, B, C, D from left to right]]
[[Image:4-Band Resistor.svg|A diagram of a 2.7&nbsp;MΩ color-coded resistor.]]
{{ordered list
 | list-style-type=upper-alpha
 | The first significant figure of component value (left side)
 | The second significant figure (some precision resistors have a third significant figure, and thus five bands).
 | The decimal multiplier (number of trailing zeroes, or power of 10 multiplier)
 | If present, indicates tolerance of value in percent (no band means 20%)
}}

In the above example, a resistor with bands of red, violet, green, and gold has first digit 2 (red; see table below), second digit 7 (violet), followed by 5 (green) zeroes: {{val|2,700,000|u=ohms}}. Gold signifies that the tolerance is ±5%.

Precision resistors may be marked with a five band system, to include three significant digits, a power of 10 multiplier (number of trailing zeroes, and a tolerance band. An extra-wide first band indicates a wire-wound resistor.<ref name="Westman_1968"/>
[[File:Resistor Color Code.svg|alt=resistor color code|thumb|Resistor color code]]
Resistors manufactured for military use may also include a fifth band which indicates component failure rate ([[Reliability engineering|reliability]]); refer to [[MIL-HDBK]]-199<ref name="MIL_HDBK_199C"/> for further details.

Tight tolerance resistors may have three bands for significant figures rather than two, or an additional band indicating [[temperature coefficient of resistance]] (TCR), in units of [[parts per million|ppm]]/[[Kelvin|K]].

All coded components have at least two value bands and a multiplier; other bands are optional.

The standard color code per [[IEC 60062:2016]] is as follows:
{{Electronic colour code}}
Resistors use various [[E series of preferred numbers#Lists|E series of preferred numbers]] for their specific values, which are determined by their [[tolerance (engineering)|tolerance]]. These values repeat for every decade of magnitude: ... 0.68, 6.8, 68, 680, ... For resistors of 20% tolerance the E6 series, with six values: 10, 15, 22, 33, 47, 68, then 100, 150, ... is used; each value is approximately the previous value multiplied by {{radic|10|6}}. For 10% tolerance resistors the E12 series, with {{radic|10|12}} as multiplier, is used; similar schemes up to E192, for 0.5% or tighter tolerance are used. The separation between the values is related to the tolerance so that adjacent values at the extremes of tolerance approximately just overlap; for example, in the E6 series {{nobr|10 + 20%}} is 12, while {{nobr|15 − 20%}} is also 12.

[[Zero ohm resistor]]s, marked with a single black band,<ref name="NZO_NIC"/> are lengths of wire wrapped in a resistor-like body which can be mounted on a [[printed-circuit board]] (PCB) by automatic component-insertion equipment. They are typically used on PCBs as insulating "bridges" where two tracks would otherwise cross, or as soldered-in [[Jumper (computing)|jumper]] wires for setting configurations.

=== Body-end-dot system ===
The "body-end-dot" or "body-tip-spot" system was used for cylindrical composition resistors sometimes still found in very old equipment (built before the Second World War); the first band was given by the body color, the second band by the color of one end of the resistor, and the multiplier by a dot or band around the middle of the resistor. The other end of the resistor was in the body color, silver, or gold for 20%, 10%, 5% tolerance (tighter tolerances were not routinely used).<ref name="FTRC_1946"/><ref name="BTS"/><ref name="RMA"/><ref name="Antique_Resistor"/>

===Examples===
[[Image:Resistors color code.jpg|right|300px|thumb|Example color-coded resistors]]
From top to bottom:
* Green, blue, black, black, brown
** 560&nbsp;ohms ±1%
* Red, red, orange, gold
** {{val|22000|u=ohms}} ±5%
* Yellow, violet, brown, gold
** 470&nbsp;ohms ±5%
* Blue, grey, black, gold
** 68&nbsp;ohms ±5%

The physical size of a resistor is indicative of the [[power (physics)|power]] it can dissipate.

There is an important difference between the use of three and of four bands to indicate resistance. The same resistance is encoded by:
*Red, red, ''orange'' = ''22'' followed by ''3'' zeroes = {{val|22000}} (excluding default, silver, or gold tolerance)
*Red, red, ''black'', ''red'' = ''220'' followed by ''2'' zeroes = {{val|22000}} (excluding brown or other band for tolerance)

===Mnemonics===
{{Further|List of electronic color code mnemonics}}

Useful [[mnemonic]]s have been created to make it easier to remember the numeric order of resistor color bands:

* '''B'''etty '''B'''rown '''R'''uns '''O'''ver '''Y'''our '''G'''arden '''B'''ut '''V'''iolet '''G'''ingerly '''W'''alks.
* '''B'''ad '''B'''ears '''R'''aid '''O'''ur '''Y'''ummy '''G'''rub '''B'''ut '''V'''eto '''G'''rey '''W'''affles.
* '''BB''' '''ROY''' from '''G'''reat '''B'''ritain has a '''V'''ery '''G'''ood '''W'''ife. 
The following example includes the tolerance codes — gold, silver and none:

* '''B'''ad '''B'''eer '''R'''ots '''O'''ut '''Y'''our '''G'''uts '''B'''ut '''V'''odka '''G'''oes '''W'''ell – '''G'''et '''S'''ome '''N'''ow.<ref name="Campbell_BUCD"/>

The colors are sorted in ascending order of visible light photon [[visible light spectrum|frequency/energy]] like in a rainbow to make them easy to remember and to reduce the significance of possible read errors due to color shifts and fading over time<!-- except for the tolerance ring -->: red (2), orange (3), yellow (4), green (5), blue (6), violet (7). Black (0) has no energy, brown (1) has a little more, white (9) has everything and grey (8) is like white, but less intense.<ref name="Clement"/>

=={{anchor|Capacitor code}}Capacitors==
Capacitors may be marked with 4 or more colored bands or dots. The colors encode the first and second most significant digits of the value in picofarads, and the third color the decimal multiplier. Additional bands have meanings which may vary from one type to another. Low-tolerance capacitors may begin with the first 3 (rather than 2) digits of the value. It is usually, but not always, possible to work out what scheme is used by the particular colors used. Cylindrical capacitors marked with bands may look like resistors.

{| class="wikitable" style="text-align:center;"
|-
! colspan="2" | Color
! Significant digits
! Multiplier
! Tolerance [%]
! Characteristic
! DC working voltage [V]
! [[Operating temperature]] [°C]
! EIA/vibration [Hz]
|-
| style="background-color:black" | &nbsp;
! Black
| 0 || 1 || — || — || — || −55 to +70 || 10 to 55
|-
| style="background-color:brown" |
! Brown
| 1 || 10 || ±1 || B || 100 || — || —
|-
| style="background-color:red" |
! Red
| 2 || 100 || ±2 || C || — || −55 to +85 || —
|-
| style="background-color:orange" |
! Orange
| 3 || {{val|1000|fmt=gaps}} || — || D || 300 || — || —
|-
| style="background-color:yellow" |
! Yellow
| 4 || {{val|10000}} || — || E || — || −55 to +125 || 10 to {{val|2000}}
|-
| style="background-color:green" |
! Green
| 5 || {{val|100000}} || ±0.5 || F || 500 || — || —
|-
| style="background-color:blue" |
! Blue
| 6 || {{val|1000000}} || — || — || — || −55 to +150 || —
|-
| style="background-color:violet" |
! Violet
| 7 || {{val|10000000}} || — || — || — || — || —
|-
| style="background-color:grey" |
! Grey
| 8 || — || — || — || — || — || —
|-
| style="background-color:white" |
! White
| 9 || — || — || — || — || — || [[Electronic Industries Alliance|EIA]]
|-
| style="background-color:gold" |
! Gold
| — || — || ±5<ref group="nb" name="NB_Tolerance"/> || — || {{val|1000}} || — || —
|-
| style="background-color:silver" |
! Silver
| — || — || ±10 || — || — || — || —
|}

Extra bands on ceramic capacitors identify the voltage rating class and temperature coefficient characteristics.<ref name="FTRC_1946"/> A broad black band was applied to some tubular paper capacitors to indicate the end that had the outer electrode; this allowed this end to be connected to chassis ground to provide some shielding against hum and noise pickup.

[[Polyester]] [[Film capacitor|film]] and "gum drop" [[tantalum electrolytic capacitor]]s may also be color-coded to give the value, working voltage and tolerance.

==={{anchor|3-dot|6-dot}}Postage stamp capacitors and war standard coding===
[[File:EIA Capacitor Color Codes.jpg|thumb|Postage-stamp [[mica capacitor]]s marked with the EIA 3-dot and 6-dot color codes, giving capacitance value, tolerance, working voltage, and temperature characteristic. This style of capacitor was used in vacuum-tube equipment.]]
Capacitors of the rectangular "postage stamp" form made for military use during World War II used ''[[American War Standard]]'' (AWS) or ''[[Joint Army-Navy]]'' (JAN) coding in six dots stamped on the capacitor. An arrow on the top row of dots pointed to the right, indicating the reading order. From left to right the top dots were: either black, indicating JAN [[mica capacitor|mica]], or silver, indicating AWS paper; first significant digit; and second significant digit. The bottom three dots indicated temperature characteristic, tolerance, and decimal multiplier. The characteristic was black for {{val|±1000|u=ppm/°C}}, brown for ±500, red for ±200, orange for ±100, yellow for −20 to +100&nbsp;ppm/°C, and green for 0 to +70&nbsp;ppm/°C.

A similar six-dot code by EIA had the top row as first, second and third significant digits and the bottom row as voltage rating (in hundreds of volts; no color indicated 500 volts), tolerance, and multiplier. A three-dot EIA code was used for 500 volt 20% tolerance capacitors, and the dots signified first and second significant digits and the multiplier. Such capacitors were common in [[vacuum tube]] equipment and in surplus for a generation after the war but are unavailable now.<ref name="ARRL77"/>

=={{anchor|Inductor code}}Inductors==
Standards IEC&nbsp;60062&nbsp;/ EN&nbsp;60062 do not define a color code for [[inductor]]s, but manufacturers of small inductors use the resistor color code, typically encoding [[inductance]] in microhenries.<ref name="TDK_Inductors"/> A white tolerance ring is used by [[TDK]] to indicate custom specifications.<ref name="TDK_Inductors"/>

==Diodes==
The part number for small [[JEDEC]] "1N"-coded diodes{{dash}}in the form "1N4148"{{dash}}is sometimes encoded as three or four rings in the standard color code, omitting the "1N" prefix. The [[1N4148 signal diode|1N4148]] would then be coded as yellow (4), brown (1), yellow (4), grey (8).

==Wire==

===Transformer===
Power [[transformer]]s used in North American vacuum-tube equipment were often color-coded to identify the leads. Black was the primary connection, red secondary for the B+ (plate voltage), red with a yellow tracer was the [[center tap]] for the B+ full-wave rectifier winding, green or brown was the heater voltage for all tubes, yellow was the filament voltage for the rectifier tube (often a different voltage than other tube heaters). Two wires of each color were provided for each circuit, and phasing was not identified by the color code.

Audio transformers for vacuum tube equipment were coded blue for the finishing lead of the primary, red for the B+ lead of the primary, brown for a primary center tap, green for the finishing lead of the secondary, black for grid lead of the secondary, and yellow for a tapped secondary. Each lead had a different color since relative polarity or phase was more important for these transformers. Intermediate-frequency tuned transformers were coded blue and red for the primary and green and black for the secondary.<ref name="ARRL77"/>

===Other===
Wires may be color-coded to identify their function, voltage class, polarity, phase or to identify the circuit in which they are used. The insulation of the wire may be solidly colored, or where more combinations are needed, one or two tracer stripes may be added. Some wiring color codes are set by national regulations, but often a color code is specific to a manufacturer or industry.

[[Building wiring]] under the US [[National Electrical Code]] and the [[Canadian Electrical Code]] is identified by colors to show energized, neutral, and grounding conductors, and to identify phases. Other color codes are used in the UK and other areas to identify building wiring or flexible cable wiring.

Mains electrical wiring, both in a building and on equipment, was once usually red for live, black for neutral, and green for earth, but this was changed as it was a hazard for color-blind people, who might confuse red and green; different countries use different conventions. Red and black are frequently used for positive and negative of battery or other single-voltage DC wiring.

[[Thermocouple]] wires and extension cables are identified by color code for the type of thermocouple; interchanging thermocouples with unsuitable extension wires destroys the accuracy of the measurement.

Automotive wiring is color-coded but standards vary by manufacturer; differing [[SAE International|SAE]] and [[DIN]] standards exist.

Modern [[personal computer]] peripheral cables and connectors are [[PC connector colors|color-coded]] to simplify connection of speakers, microphones, mice, keyboards and other peripherals, usually according to coloring schemes following recommendations such as [[PC System Design Guide]], [[PoweredUSB]], [[ATX]], etc.

A common convention for wiring systems in industrial buildings is: black jacket – AC less than {{val|1000|u=volts|fmt=commas}}, blue jacket – DC or communications, orange jacket – medium voltage {{val|2300|fmt=commas}} or {{val|4160|u=V|fmt=commas}}, red jacket {{val|13800|u=V|fmt=commas}} or higher. Red-jacketed cable is also used for relatively low-voltage [[fire alarm]] wiring, but has a much different appearance.

Local area network cables may also have non-standardised jacket colors identifying, for example, process control network vs. office automation networks, or to identify redundant network connections, but these codes vary by organization and facility.

==See also==
{{Commons category|Electronic color code}}
* [[E series of preferred numbers]] (IEC 60063){{dash}}series of preferred resistance and capacitance values
* [[Color code]]
* [[Electrical wiring]]{{dash}}AC power wiring inside buildings, including standard color codes

==Notes==
{{reflist|group="nb"|refs=
<ref group="nb" name="NB_Tolerance">±5% or ±0.5&nbsp;pF, whichever is greater.</ref>
}}

==References==
<references>
<ref name="ARH_1932_1">{{cite journal |title=Color coding |journal=[[Service - A Monthly Digest of Radio and Allied Maintenance]] |date=April 1932 |volume=1 |number=3 |editor-first1=John F. |editor-last1=Rider |editor-link1=John F. Rider |editor-first2=M. L. |editor-last2=Muhleman |publisher=[[John F. Rider Publications, Inc.]] |location=New York City, NY, USA |page=62 |url=https://www.americanradiohistory.com/Archive-Service-Magazine/30s/Service-1932-04.pdf |access-date=2019-11-15
|quote=Color coding of resistances used in receivers is not always according to the standard recommended by the [[Radio Manufacturers Association|RMA]]. Most of the manufacturers now are using this code. The following is a partial tabulation of receiver manufacturers and comments concerning their use of the body, tip and dot system. […]}} (NB. Part 1/2 of a list of when each radio manufacturer first started using RMA color coded resistors.)</ref>
<ref name="ARH_1932_2">{{cite journal |title=Color coding - Continued from April issue |journal=[[Service - A Monthly Digest of Radio and Allied Maintenance]] |date=May 1932 |volume=1 |number=4 |editor-first1=John F. |editor-last1=Rider |editor-link1=John F. Rider |editor-first2=M. L. |editor-last2=Muhleman |publisher=[[John F. Rider Publications, Inc.]] |location=New York City, NY, USA |page=89 |url=https://www.americanradiohistory.com/Archive-Service-Magazine/30s/Service-1932-05.pdf |access-date=2019-11-15}} (NB. Part 2/2 of a list of when each radio manufacturer first started using [[Radio Manufacturers Association|RMA]] color coded resistors.)</ref>
<ref name="JEDEC_EIA">{{cite web |title=JEDEC History |publisher=[[JEDEC]] |url=http://www.jedec.com/join_jedec/history.cfm |access-date=2007-09-29 |url-status=dead |archive-url=https://web.archive.org/web/20070929155400/http://www.jedec.com/join_jedec/history.cfm |archive-date=2007-09-29}}</ref>
<ref name="IEC_60062_2016">{{cite web |title=IEC 60062:2016-07 |date=July 2016 |edition=6 |url=https://www.sis.se/api/document/preview/8021442/ |access-date=2018-07-23 |url-status=live |archive-url=https://web.archive.org/web/20180723125246/https://www.sis.se/api/document/preview/8021442/ |archive-date=2018-07-23}} [https://webstore.iec.ch/publication/25395]</ref>
<ref name="EIA_RS-279">{{cite book |title=EIA RS-279: Color code for film resistors |publisher=[[Electronic Industries Alliance]] |date=1963-08-01}}</ref>
<ref name="MIL_HDBK_199C">{{cite web |title=MIL-HDBK-199C |url=https://tomwwolf.files.wordpress.com/2013/12/mil-hdbk-199c.pdf}}</ref>
<ref name="NZO_NIC">{{cite web |title=NZO series zero-ohm resistors |publisher=NIC Components Corp. |url=http://www.niccomp.com/products/series.asp?cate=Resistives&type=Leaded&series=NZO |archive-url=https://web.archive.org/web/20090104143106/http://www.niccomp.com/products/series.asp?cate=Resistives&type=Leaded&series=NZO |archive-date=2009-01-04}}</ref>
<ref name="TDK_Inductors">{{cite web |title=RF General |publisher=[[TDK]] |url=https://en.tdk.eu/download/531410/59a5850434250d35b39a06d5c80bf362/pdf-rfgeneral.pdf}}</ref>
<ref name="Campbell_BUCD">{{cite web |url=http://bradley.bradley.edu/~campbell/mnemonic.html |title=The Mnemonics Page |author-first=Dean |author-last=Campbell |publisher=[[Bradley University]] Chemistry Department}}</ref>
<ref name="FTRC_1946">{{cite book |title=Reference Data for Radio Engineers |chapter=Chapter 3: Audio and radio design |editor-first1=Harold H. |editor-last1=Buttner
|editor-first2=H. T. |editor-last2=Kohlhaas |editor-first3=F. J. |editor-last3=Mann |publisher=[[Federal Telephone and Radio Corporation]] (FTR) |edition=2 |date=1946 |pages=52, 57 |url=http://www.tubebooks.org/Books/FTR_ref_data.pdf |access-date=2020-01-03 |url-status=live |archive-url=https://web.archive.org/web/20180516201551/http://www.tubebooks.org/Books/FTR_ref_data.pdf |archive-date=2018-05-16}}</ref>
<ref name="Clement">{{cite book |title=Electrical Engineering Science |author-first1=Preston R. |author-last1=Clement |author-first2=Walter Curtis |author-last2=Johnson |publisher=[[McGraw-Hill]] |date=1960 |page=[https://archive.org/details/electricalengine0000clem/page/115 115] |url=https://archive.org/details/electricalengine0000clem |url-access=registration}}</ref>
<ref name="BTS">{{cite web |title=How To Read Old Style Resistors |date=2006-10-03 |url=http://www.philipstorr.id.au/radio/technical/BTS_Resistors.pdf |access-date=2016-12-19 |url-status=live |archive-url=https://web.archive.org/web/20161219160419/http://www.philipstorr.id.au/radio/technical/BTS_Resistors.pdf |archive-date=2016-12-19}}</ref>
<ref name="RMA">{{cite web |title=RMA Resistor and Flexible Resistor Color Codes |url=http://www.radioremembered.org/rescode.htm |access-date=2016-12-19 |url-status=live |archive-url=https://web.archive.org/web/20161219160621/http://www.radioremembered.org/rescode.htm |archive-date=2016-12-19}}</ref>
<ref name="Antique_Resistor">{{cite web |title=The Antique Resistor Color Code |url=https://all-unique.com/PDF/Antique_Resistor_Color_Code.pdf |access-date=2016-12-19 |url-status=live |archive-url=https://web.archive.org/web/20161219160711/https://all-unique.com/PDF/Antique_Resistor_Color_Code.pdf |archive-date=2016-12-19}}</ref>
<ref name="ARRL77">{{cite book |editor-first=Tony |editor-last=Dorbuck |title=The Radio Amateur's Handbook |edition=5 |date=1978 |publisher=[[The American Radio Relay League]] |location=Connecticut, USA |orig-year=1977 |id=no ISBN |lccn=41-3345 |pages=553–554}}</ref>
<ref name="Westman_1968">{{cite book |editor-first=H. P. |editor-last=Westman |title=Reference Data for Radio Engineers |date=1968 |edition=5 |publisher=[[International Telephone & Telegraph|ITT]] / [[Howard W. Sams]] |lccn=43-14665<!-- correct? --> |pages=5-8–5-10}}</ref>
</references>

==External links==
; Online resistor calculators
:* [http://www.resistorcalc.net Multi-purpose resistor code converter] (4 and 5 band, mobile-friendly, shows nearest standard value)
:* [https://samstechlib.com/46436194/en/read/6_Band_Resistor_Color_Codes 6 band resistor color code calculator] (easy lookup, 4 and 5 band calculators also available)
; Historical charts
:* [https://stevenjohnson.com/cardboard/wheelcharts.htm Wheel charts]
:* [https://stevenjohnson.com/cardboard/refcharts.htm Reference charts]

[[Category:Color codes]]
[[Category:Electrical components|color code]]
[[Category:Electronic engineering|color code]]
[[Category:Resistive components]]
[[Category:Mnemonics]]

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