Electronics Components: How to Interpret Resistor Color Codes - dummies

Electronics Components: How to Interpret Resistor Color Codes

By Doug Lowe

Resistance is an essential element of every electronic circuit, so you will work with a lot of resistors as you explore electronics. You can determine the resistance provided by a resistor by examining the color codes that are painted on the resistor.

These little stripes of bright colors indicate two important factoids about the resistor: its resistance in ohms and its tolerance, which indicates how close to the indicated resistance value the resistor actually is.

Most resistors have four stripes of color. The first three stripes indicate the resistance value, and the fourth stripe indicates the tolerance. Some resistors have five stripes of color, with four representing the resistance value and the last one the tolerance.

If you’re uncertain from which side of the resistor to read the colors, start with the side closest to the color stripe. The first stripe is usually painted very close to the edge of the resistor; the last stripe isn’t as close to the edge.

Read a resistor’s value

Here are the values assigned to the colors:

Color Digit Multiplier
Black 0 1
Brown 1 10
Red 2 100
Orange 3 1 k
Yellow 4 10 k
Green 5 100 k
Blue 6 1 M
Violet 7 10 M
Gray 8 100 M
White 9 1,000 M
Gold 0.1
Silver 0.01

Now you can use those digits and multipliers to follow this procedure for determining the value of a resistor with four stripes:

  1. Orient the resistor so you can read the stripes properly.

    You should read the stripes from left to right. The first stripe is the one that’s closest to one end of the resistor. If this stripe is on the right side of the resistor, turn the resistor around so the first stripe is on the left.

  2. Look up the color of the first stripe to determine the value of the first digit.

    For example, if the first stripe is yellow, the first digit is 4.

  3. Look up the color of the second stripe to determine the value of the second digit.

    For example, if the first stripe is violet, the second digit is 7.

  4. Look up the color of the third stripe to determine the multiplier.

    For example, if the third stripe is brown, the multiplier is 10.

  5. Multiply the two-digit value by the multiplier to determine the resistor’s value.

    For example, 47 times 10 is 470. Thus, a yellow-violet-brown resistor is 470 Ω.

Here are a few examples that should help you understand how to read resistor codes:

Color Stripes Digit Values Multiplier (in Ohms) Resistor Value
Brown – black – brown 10 10 100 Ù
Brown – black – red 10 100 1 kÙ
Red – red – orange 22 1 k 22 kÙ
Red – red – yellow 22 10 k 220 kÙ
Yellow – violet – black 47 0.1 47 Ù

Resistor tolerance

The value indicated by the stripes on a resistor provides an estimate of resistance. The exact resistance varies by a percentage that depends on the tolerance factor of the resistor.

For example, a 22 kΩ resistor with a 5% tolerance actually has a value somewhere between 5% above and 5% below 22 kΩ, which works out to somewhere between 20.9 and 23.1 kΩ. A 470 Ω resistor with a 10% tolerance has an actual value somewhere between 423 and 517Ω.

Why the approximations? It costs more money to manufacture resistors to very close tolerances, and for most electronic circuits, a 5% or 10% margin of error is perfectly acceptable.

If your application demands higher precision, you can spend a bit more money to buy higher-tolerance resistors. But 5%- or 10%- tolerance resistors are fine for most work.

The tolerance of a resistor is indicated in the resistor’s last color stripe:

Color Tolerance
Brown 1%
Red 2%
Orange 3%
Yellow 4%
Gold 5%
Silver 10%
Black 20%