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Activity 1.1.4

Resistor Color Code & Component Identification

ResistorsColor CodeComponents

Read and interpret 4-band resistor color codes, calculate resistor values, identify common components, and use a DMM to verify values.
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Resistors are the most common passive component. They oppose current flow, protect sensitive components, and set circuit values.

What resistors do

1

Limit current to protect LEDs and other components

2

Divide voltages in sensor circuits

3

Set bias conditions in transistor circuits

4

Pull-up/pull-down functions in digital circuits

Common types

Carbon filmBrown±5%
Metal filmBlue±1%
WirewoundCeramicHigh power
SMDChipTiny
Power rating: Physical size determines how much power (watts) a resistor can safely dissipate. 1/4W (0.25W) is most common in labs. Exceeding the rating causes overheating and failure.

The color bands on a resistor encode its value. Learning this code is a fundamental skill — you'll use it every time you pick a resistor from the parts bin.

4-band color code

Black
digit 0
×1
Brown
digit 1
×10
Red
digit 2
×100
Orange
digit 3
×1k
Yellow
digit 4
×10k
Green
digit 5
×100k
Blue
digit 6
×1M
Violet
digit 7
×10M
Gray
digit 8
—
White
digit 9
—

Tolerance bands

Gold
±5%
Most common
Silver
±10%
Common
None
±20%
Rare

How to read bands

[Band1][Band2] × [Band3] ± [Band4]
1 Find the tolerance band (gold/silver) — it's separated from the others
2 Start reading from the opposite end
3 Band 1 = first digit, Band 2 = second digit
4 Band 3 = multiplier (number of zeros to add)
5 Band 4 = tolerance

See how the bands translate to a value. Each example shows the resistor, the bands, and the math.

Example 1
Band 1 Band 2 Band 3 Band 4 Brown=1 Black=0 ×100 ±5%
10 × 100 = 1,000Ω = 1kΩ ±5%
Range: 950Ω – 1,050Ω
Example 2
Band 1 Band 2 Band 3 Band 4 Red=2 Red=2 ×10 ±10%
22 × 10 = 220Ω = 220Ω ±10%
Range: 198Ω – 242Ω
Example 3 — Gold as multiplier
Band 1 Band 2 Band 3 Band 4 Yellow=4 Violet=7 ×0.1 ±0.25%
47 × 0.1 = 4.7Ω = 4.7Ω ±0.25%
Precision resistor — gold multiplier = ×0.1

Drag the correct color bands onto the resistor to match the target value. Start with assemble mode to build familiar resistors, then switch to identify mode for a challenge.

Color codes give you the intended value, but actual components vary. Always verify with a DMM before using in a circuit.

Procedure

1
Set mode
Turn dial to resistance mode (Ω symbol)
2
Touch probes
Red to one lead, black to the other (either direction)
3
Read display
Wait for reading to stabilize, note the value
4
Compare
Check against color code value and tolerance range

Tips for accurate readings

1

Remove resistor from circuit if possible

2

If in-circuit, disconnect at least one lead

3

Don't touch both probes — body resistance affects reading

4

Some DMMs auto-range; others need manual selection

Out of tolerance? If your DMM reading is outside the tolerance range, the resistor may be damaged or counterfeit. Set it aside.

Capacitors use different marking schemes. Electrolytic caps print the value directly. Ceramic caps use a 3-digit code.

Ceramic capacitor codes

First two digits × 10third = pF
Digits
Value in picofarads
Third
Multiplier (number of zeros)

Common values

101
100 pF
0.1 nF
102
1,000 pF
1 nF
103
10,000 pF
10 nF
104
100,000 pF
100 nF
223
22,000 pF
22 nF
474
470,000 pF
470 nF
Danger: Electrolytic capacitors can hold a charge even when disconnected. They can shock you or damage circuits if discharged improperly. Long lead = positive, short lead = negative.