Resistors are among the most fundamental components in electronics. Whether you are designing a circuit, troubleshooting a PCB, or teaching students about Ohm’s law, resistors are everywhere. But unlike capacitors or ICs that often have their values printed directly on them, resistors are usually marked with colour bands. These bands encode the resistance value, tolerance, and sometimes reliability or temperature coefficient.
Understanding resistor colour codes is essential for anyone
working with electronics. In this blog, we’ll dive deep into how to calculate
resistor values using 4-band, 5-band, and other variations, ensuring you
don’t miss a single detail.
The Basics of Resistor Colour Codes
Resistor colour codes follow a standardized system. Each colour corresponds to a number, multiplier, or
tolerance.
Here’s the master colour chart:
|
Colour |
Digit Value |
Multiplier |
Tolerance |
|
Black |
0 |
×10⁰ (1) |
— |
|
Brown |
1 |
×10¹ (10) |
±1% |
|
Red |
2 |
×10² (100) |
±2% |
|
Orange |
3 |
×10³ (1k) |
— |
|
Yellow |
4 |
×10⁴ (10k) |
— |
|
Green |
5 |
×10⁵ (100k) |
±0.5% |
|
Blue |
6 |
×10⁶ (1M) |
±0.25% |
|
Violet |
7 |
×10⁷ (10M) |
±0.1% |
|
Grey |
8 |
×10⁸ |
±0.05% |
|
White |
9 |
×10⁹ |
— |
|
Gold |
— |
×10⁻¹ (0.1) |
±5% |
|
Silver |
— |
×10⁻² (0.01) |
±10% |
|
None |
— |
— |
±20% |
How to Read Resistor Colour Bands
Resistors typically have 4, 5, or 6 bands. The number
of bands determines how precise the resistor value is and how much information
is encoded.
1. 4-Band Resistors (Most Common)
- Band
1: First digit
- Band
2: Second digit
- Band
3: Multiplier
- Band
4: Tolerance
Example: Colour bands: Red (2), Violet (7), Yellow
(×10⁴), Gold (±5%)
Calculation:
27×10^4 = 270,000 Ω = 270 kΩ
Tolerance: ±5% → Actual value can range between 256.5kΩ and
283.5kΩ.
2. 5-Band Resistors (Precision Resistors)
- Band
1: First digit
- Band
2: Second digit
- Band
3: Third digit
- Band
4: Multiplier
- Band
5: Tolerance
Example: Colour bands: Brown (1), Black (0), Black
(0), Red (×10²), Brown (±1%) Calculation:
100 × 10^2 = 10,000 Ω = 10 kΩ
Tolerance: ±1% → Actual value between 9.9kΩ and 10.1kΩ.
3. 6-Band Resistors (High Precision + Temperature
Coefficient)
- Band
1: First digit
- Band
2: Second digit
- Band
3: Third digit
- Band
4: Multiplier
- Band
5: Tolerance
- Band
6: Temperature coefficient (ppm/°C)
Temperature coefficient indicates how much the resistance
changes with temperature. For example, Blue (10 ppm/°C) means resistance
changes by 10 parts per million per degree Celsius.
Step-by-Step Method to Calculate Resistor Value
- Identify
the number of bands (4, 5, or 6).
- Read
from left to right (the tolerance band is usually spaced farther apart
or metallic like gold/silver).
- Convert
colours to digits using the chart.
- Apply
the multiplier.
- Note
the tolerance (and temperature coefficient if present).
Practical Examples
Example 1: 4-Band Resistor
Bands: Green, Blue, Red, Gold
- Digits:
5 (Green), 6 (Blue) → 56
- Multiplier:
Red = ×100 → 5600Ω
- Tolerance:
Gold = ±5%
Final Value: 5.6kΩ ±5%
Example 2: 5-Band Resistor
Bands: Orange, Orange, Black, Brown, Brown
- Digits:
3 (Orange), 3 (Orange), 0 (Black) → 330
- Multiplier:
Brown = ×10 → 3300Ω
- Tolerance:
Brown = ±1%
Final Value: 3.3kΩ ±1%
Example 3: 6-Band Resistor
Bands: Blue, Grey, Black, Red, Brown, Blue
- Digits:
6 (Blue), 8 (Grey), 0 (Black) → 680
- Multiplier:
Red = ×100 → 68,000Ω
- Tolerance:
Brown = ±1%
- Temp
Coefficient: Blue = 10 ppm/°C
Final Value: 68kΩ ±1%, 10
ppm/°C
Special Cases
- Zero
Ohm Resistors: These are essentially wire links, often marked with a
single black band.
- High
Precision Resistors: Often use 5 or 6 bands with tighter tolerances
(±0.1%, ±0.05%).
- Surface-Mount
Resistors (SMD): These don’t use colour codes; instead, they have
numerical codes like “472” (47 × 10² = 4700Ω).
Tips for Reading Resistor Codes
- Orientation
matters: The tolerance band (gold/silver) is usually spaced apart.
Start reading from the opposite end.
- Lighting
helps: Colours can fade or look similar (red vs. orange, blue vs.
violet). Use good lighting or a magnifier.
- Double-check
with a multimeter: Always verify resistor values with a digital
multimeter, especially if colours are unclear.
- Practice
makes perfect: The more you decode, the faster you’ll recognize values
instantly.
Why Different Band Systems Exist
- 4-Band:
Standard resistors with moderate tolerance (±5%, ±10%).
- 5-Band:
Precision resistors with tighter tolerance (±1%, ±0.5%).
- 6-Band:
High-precision resistors used in sensitive applications like
instrumentation, where temperature stability matters.
Real-World Applications
- Electronics
Education: Teaching resistor codes is a staple in beginner electronics
courses.
- PCB
Troubleshooting: Identifying burnt, or mismatched resistors quickly
saves repair time.
- Design
& Prototyping: Choosing resistors with correct tolerance ensures
circuit stability.
- Industrial
Automation: Precision resistors are critical in sensors, measurement
devices, and control systems.
Mnemonics for Remembering Colour Codes
A popular mnemonic for digits 0–9:
“BB ROY of Great
Britain had a Very Good Wife”
- Black
(0), Brown (1), Red (2), Orange (3), Yellow (4), Green (5), Blue (6),
Violet (7), Grey (8), White (9).
For tolerance:
- Gold
= ±5%, Silver = ±10%, None = ±20%.
Conclusion
Resistor colour codes may look intimidating at first, but
once you understand the system, they become second nature. By mastering 4-band,
5-band, and 6-band resistor codes, you can quickly calculate resistance
values, tolerances, and even temperature coefficients.
Whether you’re a student learning electronics, an engineer
designing circuits, or a hobbyist tinkering with Arduino projects, knowing how
to decode resistor colour bands is a skill you’ll use constantly. And remember
— when in doubt, verify with a multimeter!