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Resistors' Color Code

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Tool to compute resistor color code. Electronic components, such as resistors, have their values designated by a color code and standardized.
Summary

3-Band Resistor Calculator

From a given value

 Find corresponding colors The closest normalized value The SMD code with 3 characters The SMD code with 4 characters

6 band resistor calculator

How to calculate the value of a resistor?

To know the value of a resistance, use an ohm-meter here 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 :

Example:

 0 Black 1 Brown 2 Red 3 Orange 4 Yellow 5 Green 6 Blue 7 Violet 8 Grey 9 White -1 Gold -2 Silver

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 next band (third or fourth) indicates a multiplication factor (more exactly a power of 10) to the number formed by the two first digits.

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 $$642 \times 10^1 \pm 1 \% = 6420 \Omega ± 1 \%$$

How to read the value of the multiplicator band?

A multiplier ring of value $$n$$ corresponds to a multiplication by $$10^n$$ (the corresponding power of 10). This is equivalent to multiply $$n$$ times by 10, or to add $$n$$ zeros.

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.

Why is there a difference between theoretical and measured value?

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.

How to compute the tolerance interval?

The tolerance interval of a resistor is calculated by a percentage of the theoretical value. The percentage applies in plus or minus of the value.

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 $$[198, 242]$$.

How to know the reading direction for colors of a resistor?

The more often, the first band is the closest to the edge. The tolerance band is sometime more spaced than the previous ones.

How to write the value of a resistor?

Generally prefixes are used for values in Ohm, k for kilo (10^3) and M for mega (10^6).

Example: 12000 Ω = 12 kΩ

Example: 3400000 Ω = 3.4 MΩ

Does a 3 band resistor exists?

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%

What are mnemonics tricks to remember colors?

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)

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