Tool to compute resistor color code. Electronic components, such as resistors, have their values designated by a color code and standardized.
Resistors' Color Code - dCode
Tag(s) : Electronics
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To know the value of a resistance, use an ohm-meter here (link) or read the color code on the resistor.
The International Norm CEI 60757 (1983) define a color code to write the value of a resistor (but also condenser, and some other electronic component).
Colors are associated to digits:
The more often, a resistor has 4 bands:
The two first band (or the three first) indicate a digit each (a digit correspond to a color)
The last one (fourth, sometimes fifth) indicates the tolerance or precision of the calculated value. When this band is absent, it means the largest tolerance: 20%.
Sometimes an additional band is coded for precise resistor, it indicates a coefficient of temperature (in ppm/Kelvin or ppm/°C)
Example: A resistor Yellow,Orange,Red, digits are: 4,3,2. The first 2 digits make the number 43. The 3rd digit 2 is the power of 10 factor. The calculation is $ 43 \times 10^2 = 4300 \Omega $
Example: A resitor Blue,Yellow,Red,Brown,Brown, so the digits are 6,4,2,1,1. The value is given by $ 642 \times 10^1 \pm 1 \% = 6420 \Omega ± 1 \% $
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Example: If the multiplier ring gives the number 3, then multiply the value given by the first rings by $ 10 ^ 3 = 1000 $.
If this ring is of gold color, the value is divided by 10, and for the color silver, divide by 100.
The measured value is never exact but must be in the tolerance interval of the resistor.
Example: A resistor of 100 Ω with a tolerance of 5% could be measured between 95 Ω and 105 Ω.
Example: A resistor of 220 ohms Ω with a tolerance of 10%. The value of the tolerance is therefore $ 220 \times 10\% = 22 $. The tolerance interval is therefore $ 220 \pm 22 $, the value is between 198 and 242, sometimes noted $ [198, 242] $.
The more often, the first band is the closest to the edge. The tolerance band is sometime more spaced than the previous ones.
Generally prefixes are used for values in Ohm (symbol Ω U+2126, coming from the greek letter Ω U+03A9), k for kilo (10^3) and M for mega (10^6).
Example: 12000 Ω = 12 kΩ
Example: 3400000 Ω = 3.4 MΩ
A resistor has a minimum of 4 bands, but sometimes, the last band is absent. As it is only about tolerance of the value found with the first 3 bands, take the highest tolerance value: 20%
Some mnemonicssentences can help to remember the colors and their values. (Some include tolerance bands Gold, Silver or None).
Example: B.B. ROY Goes Bombay Via Gateway With Genelia and Susanne.
B. (BLACK) B. (BROWN) ROY (RED-ORANGE-YELLOW) Goes (GREEN) Bombay (BLUE) Via (VIOLET) Gateway (GREY) With (WHITE) Genelia (GOLD) and Susanne (SILVER).
Example: Bad Beer Rots Our Young Guts But Vodka Goes Well – Get Some Now.
Bad (BLACK) Beer (BROWN) Rots (RED) Our (ORANGE) Young (YELLOW) Guts (GREEN) But (BLUE) Vodka (VIOLET) Goes (GREY) Well (WHITE) – Get (GOLD) Some (SILVER) Now (NONE).
Example: Big Boys Race Our Young Girls But Violet Generally Wins.
Big (BLACK) Boys (BROWN) Race (RED) Our (ORANGE) Young (YELLOW) Girls (GREEN) But (BLUE) Violet (VIOLET) Generally (GREY) Wins (WHITE).
Example: Better Be Right Or Your Great Big Venture Goes West.
Better (BLACK) Be (BROWN) Right (RED) Or (ORANGE) Your (YELLOW) Great (GREEN) Big (BLUE) Venture (VIOLET) Goes (GREY) West (WHITE).
Example: Better Be Right Or Your Great Big Vacation Goes Wrong.
Better (BLACK) Be (BROWN) Right (RED) Or (ORANGE) Your (YELLOW) Great (GREEN) Big (BLUE) Vacation (VIOLET) Goes (GREY) Wrong (WHITE).
Example: Big Brown Rabbits Often Yield Great Big Vocal Groans When Gingerly Slapped Needlessly
Big (BLACK) Brown (BROWN) Rabbits (RED) Often (ORANGE) Yield (YELLOW) Great (GREEN) Big (BLUE) Vocal (VIOLET) Groans (GREY) When (WHITE) Gingerly (GOLD) Slapped (SILVER) Needlessly (NONE)
The role of a resistance is to withstand/resist the passage of the current. The higher the value of a resistor, the more it resists the current flow in an electronic circuit.