Electronics: Reading Resistor and Capacitor Codes - dummies

Electronics: Reading Resistor and Capacitor Codes

By Cathleen Shamieh

Part of Electronics For Dummies Cheat Sheet

Electronics can sometimes be difficult to decipher. By decoding the colorful stripes sported by many resistors and the alphanumeric markings that appear on certain types of capacitors, you can determine the nominal value and tolerance of the specific component.

Resistor color codes

Many resistor casings contain color bands that represent the nominal resistance value and tolerance of the resistor. You translate the color and position of each band into digits, multipliers, and percentages.

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The table that follows outlines the meaning of the resistor color bands.

Color 1st Digit 2nd Digit Multiplier Tolerance
Black 0 0 x1 ±20%
Brown 1 1 x10 ±1%
Red 2 2 x100 ±2%
Orange 3 3 x1,000 ±3%
Yellow 4 4 x10,000 ±4%
Green 5 5 x100,000 n/a
Blue 6 6 x1,000,000 n/a
Violet 7 7 x10,000,000 n/a
Gray 8 8 x100,000,000 n/a
White 9 9 n/a n/a
Gold n/a n/a x0.1 ±5%
Silver n/a n/a x0.01 ±10%

Capacitor value reference

In electronic circuits, the value of a capacitor can be determined by a two- or three-digit code that appears on its casing. The following table outlines values for some common capacitors.

Marking Value
nn (a number from 01 to 99) or nn0 nn picofarads (pF)
101 100 pF
102 0.001 µF
103 0.01 µF
104 0.1 µF
221 220 pF
222 0.0022 µF
223 0.022 µF
224 0.22 µF
331 330 pF
332 0.0033 µF
333 0.033 µF
334 0.33 µF
471 470 pF
472 0.0047 µF
473 0.047 µF
474 0.47 µF

Capacitor tolerance codes

In electronic circuits, the tolerance of capacitors can be determined by a code that appears on the casing. The code is a letter that often follows a three-digit number, for instance, the Z in 130Z. The following table outlines common tolerance values for capacitors. Note that the letters B, C, and D represent tolerances in absolute capacitance values, rather than percentages. These three letters are used on only very small (pF range) capacitors.

Code Tolerance
B ± 0.1 pF
C ± 0.25 pF
D ± 0.5 pF
F ± 1%
G ± 2%
J ± 5%
K ± 10%
M ± 20%
Z +80%, –20%