Resistor Color Code


Resistor Color Code

The resistor color code refers to the bands of color on carbon composition resistors (CCR) or axial lead resistors. A resistor is an electrical component with two terminals that serves several functions in a circuit, such as reducing current, terminating transmission, adjusting signal levels, and biasing active elements. So, using the right one for a situation is important. But, how do you read one and what do the resistor color codes mean?

The Resistor Color Code Table

It’s all about the color and its placement:

1st Digit2nd Digit3rd DigitDecimal
Multiplier
ToleranceTemperature Coefficient
(ppm/°C)
Silver0.01±10% (K)
Gold0.1±5% (J)
Black0001250 (U)
Brown11110±1% (F)100 (S)
Red222100±2% (G)50 (R)
Orange3331000±3%15 (P)
Yellow44410k±4%25 (Q)
Green555100k±0.5% (D)20 (Z)
Blue6661M±0.25% (C)10 (Z)
Violet77710M±0.1% (B)5 (M)
Gray888x108±0.05% (A)1 (K)
White988x109

The third significant digit only applies if there are 5 or 6 bands. The tolerance and temperature coefficient correspond to either colored bands or else to printed letters.

How to Read a Resistor

A typical axial resistor has anywhere from 3 to 6 color bands. You read a resistor color code from left to right. “Left” is the side that has the most bands or the opposite side of any metallic paint. Often, there is a space after the bands corresponding to digits and multiplier. Sometimes figuring out left and right is a bit tricky, because yellow and gray replace silver and gold in high-voltage resistors.

How to Read a Resistor
Read a resistor from left to right, starting with the side with the most bands. For example, this resistor is 1000 ohms with a tolerance of 5%. It is brown, black, red, gold.

Once you know which way you’re reading the resistor, count the bands:

Three and Four Band Resistors

On these resistors, the first two bands are the digits for the resistance in ohms (Ω). The third band is a multiplier in units of 10. The fourth band on a four-band resistor is its tolerance. A three-band resistor has a default tolerance of ±20%.

For example, a four-band resistor with the colors brown, red, green, gold has the digits 1 and 2, a multiplier of 105, and a tolerance of ±5%. Its resistance is 12 x 105 Ω or 1200 kΩ ±5%.

Five and Six Band Resistors

In five-band and six-band resistors, the third band is an additional significant digit. The fourth band is the multiplier and the fifth band is the tolerance. The sixth band indicates the temperature coefficient (ppm/K) specification. The most common color for this band is brown, indicating that the resistance varies by 0.1% for every 10 °C temperature change.

Mnemonics for Remembering the Resistor Color Code

  • 0 – Black
  • 1 – Brown
  • 2 – Red
  • 3 – Orange
  • 4 – Yellow
  • 5 – Green
  • 6 – Blue
  • 7 – Violet
  • 8 – Gray
  • 9 – White

Here are a few mnemonic devices for remembering the order of the resistor color code. The bold letter corresponds to the first letter of a color, which matches a number:

  • Big Boys Race Our Young Girls But Violet Generally Wins
  • Beach Bums Rarely Offer You Gatorade But Very Good Water
  • BB ROY of Great Britain had a Very Good Wife
  • Better BRight OYour Great Big Venture Goes West
  • Better Buy Resistors OYour Grid Bias Voltages GWest (from the vacuum-tube era)

For resistors, the colors start with black and brown, and end with gray and finally white. If you get confused about all of the “B” colors, remember the order of visible colors in the spectrum: ROY G BIV (except without the indigo).

Military Reliability Band

While uncommon in commercial electronics, some resistors for military use include a reliability band. This band specifies the failure rate percentage per thousand hours. This is the failure rate for 50% of the rated wattage. Here, it’s not the color of the band, but the letter stamped on it. M stands for a 1% failure rate, P is is a 0.1% failure rate, R is a 0.01% failure rate, and S is a 0.001% failure rate.

Single Black Band Resistor

A resistor that only has a single black band is a zero-ohm resistor. Basically, it’s just a wire that connects two points on a circuit board.

Body-Tip-Dot Resistor Color Code

Resistors from the early 20th century use a different system for color coding. Here, the base or body color represents the first digit. A second color on the resistor tip is the second digit. A dot (or sometimes band) in the middle of the resistor is the decimal multiplier. The colors have the same numerical meaning as they do today and the default tolerance is 20%. Close-tolerance resistors have silver (±10%) or gold (±5%) paint on one end.

SMT Resistors

Surface mounted resistors are larger than axial resistors. They use standard-tolerance surface-mount technology (SMT) that relies on a three digit code rather than color for indicating resistance. The first two digits are the first two significant digits of the resistance, while the third digit is the power of ten multiplier.

For example, 332 means 33 x 102 Ω or 3300 Ω while 105 means 10 x 105 Ω or 1 M Ω.

However, resistances lower than 10 Ω use the letter “R” to indicate the decimal point. For example, 4R6 means 4.6 Ω.

References

  • Buttner, Harold H.; Kohlhaas, H. T.; Mann, F. J., eds. (1946). “Chapter 3: Audio and radio design”. Reference Data for Radio Engineers (2nd ed.). Federal Telephone and Radio Corporation (FTR).
  • International Electrotechnical Commission (2016). “IEC 60062:2016-07” (6.0 ed.).
  • L3Harris (2020). “LMS 11-12 Electrical Component Identification.” Military Training Procedure.
  • Morris, C. G. (ed.) (1992). Academic Press Dictionary of Science and Technology. Gulf Professional Publishing. ISBN 0122004000.