How to read resistor color code？

This article will teach you to easily identify the color coding of resistors and quickly and accurately calculate resistance values!

What is Resistor Colour Code?

Resistors are indispensable components in electronic circuits. Since the small size of some resistors makes it difficult to directly print resistance values, a color coding system is often used to indicate resistance values, tolerances, and even temperature coefficients. This system indicates the relevant parameters by means of colored ring bands, with each color corresponding to a specific number, for quick identification and calculation. Depending on the number of color bands (commonly 3, 4, 5, or 6), the way to read them varies slightly.

Resistor Color Code Chart

Below is a resistor color coding table that can be used to quickly cross-reference the numbers, multiples and parameters corresponding to the color rings.

How to read resistor color code?

Read the resistor's color rings from left to right; the leftmost ring is the most important and is the effective number or multiplier, and the ring on the right indicates the tolerance. The number and order of the resistor's ring bands helps to identify its type.

3-Band Resistor

A 3-ring resistor is simpler, with the first two color rings representing the first two digits of the resistor value, and the third ring representing the multiplier, i.e., multiplied by 10ⁿ (power of 10). Without the fourth color ring, the default tolerance is ±20%.

Example: Red-Red-Green Color Ring Resistor
Red = 2, Red = 2, Green = 10⁵
Resistance value = 22 x 10⁵Ω = 2.2 MΩ (±20%)

4-Band Resistor

4-Ring Resistors are the most common type of resistor. The first two color rings represent the first two digits of the resistance value, the third ring represents the multiplier, and the fourth ring represents the tolerance, i.e., the deviation of the actual resistance value from the nominal resistance value.
- Gold: Tolerance ±5
- Silver: Tolerance ±10

Example: Yellow-Purple-Red-Gold Color Ring Resistors
Yellow = 4, Purple = 7, Red = 10², Gold = ±5
Resistance value = 47 x 10²Ω = 4.7 kΩ (±5%)

5-Band Resistor

Five-ring resistors have an additional effective number on top of the four-ring resistors, making resistance measurements more accurate. The first three color rings are effective numbers, the fourth ring is the multiplier, and the fifth ring indicates the tolerance.

Example: Brown-Brown-Orange-Red-Purple Ring Resistor
Brown = 1, Brown = 1, Orange = 3, Red = 10² , Purple = ±0.1%
Resistance value = 113 x 10²Ω = 11.3 kΩ (±0.1%)

6-Band Resistor

A six-ring resistor is similar to a five-ring resistor with the addition of a temperature coefficient ring, which is used to represent the amount of change in resistance with temperature.

Example: Brown-Green-Red-Black-Blue-Red Color Ring Resistors
Brown = 1, Green = 5, Red = 2, Black = 10⁰, Blue = ±0.25%, Red = 50 ppm/°C
Resistance = 152 x 10⁰Ω = 152Ω (±0.25%), 50 ppm/°C

Color Code Exceptions

Zero Ohm Resistor: This resistor has only one black band and actually functions as a wire to connect two points on a circuit board, similar to a jumper wire. It looks like a resistor but has no resistor function.
High Voltage Resistors: In order to avoid contamination by metal particles, high voltage resistors usually have the gold and silver tolerance bands replaced with yellow and gray. Five Band Resistors with Gold/Silver Fourth Band: Some special or older resistors may have a gold or silver fourth band to indicate tolerance, usually for specific applications.
Reliability Bands: Some military grade resistors will have additional reliability bands indicating the failure rate of the resistor (percentage per 1000 hours). This design is less common in commercial applications.

Tip

Read from left to right: the leftmost ring of the resistor indicates the effective number and is usually near the wire; the gold or silver colored ring is usually located on the right side and indicates the tolerance.
Check the tolerance: If the fourth band has no color band, the default tolerance is ±20%. Use a multimeter: If the color rings are ambiguous, use a multimeter to more accurately measure the resistance value.

Frequently Asked Questions

Who invented the resistor color code?
The resistor color coding system was invented by the Radio Manufacturers Association (RMA) in the 1920s.
Why are resistors color coded?
Due to the small size of some resistors, it is difficult to print directly on the resistor value. Color coding makes it easy to quickly identify the resistor value and its tolerance.
How to Remember Resistor Color Codes?
Using the mnemonic “BB ROY of Great Britain had a Very Good Wife”, in the mnemonic, the capital letters represent the first letter of the color of the resistor color coded, and the order in which they appear represents the numbers 0 through 9.