How to Read Resistor Color Codes: A Complete Guide
Master the resistor color code system with this comprehensive guide covering 4-band and 5-band reading, tolerance calculations, and common pitfalls.
The Color-to-Digit Mapping
Every resistor color corresponds to a specific digit, multiplier, or tolerance value. This is the foundation you must memorize or keep as a reference:
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1k | — |
| Yellow | 4 | ×10k | — |
| Green | 5 | ×100k | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Violet | 7 | ×10M | ±0.1% |
| Grey | 8 | — | ±0.05% |
| White | 9 | — | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Reading 4-Band Resistors
The 4-band system is the most common for general-purpose resistors. The first two bands give significant digits, the third is the multiplier, and the fourth is tolerance:
Example: Brown-Black-Red-Gold = (1 × 10 + 0) × 100 = 1,000 Ω ±5% = 1 kΩ ±5%
Example: Yellow-Violet-Orange-Silver = (4 × 10 + 7) × 1,000 = 47,000 Ω ±10% = 47 kΩ ±10%
Reading 5-Band Resistors
Precision resistors use five bands. The first three bands are significant digits, the fourth is the multiplier, and the fifth is tolerance:
Example: Brown-Black-Black-Brown-Brown = (1 × 100 + 0 × 10 + 0) × 10 = 1,000 Ω ±1% = 1 kΩ ±1%
Notice how the same 1 kΩ value is expressed differently: the 4-band version uses two digits (10) with a ×100 multiplier, while the 5-band version uses three digits (100) with a ×10 multiplier. The 5-band version achieves ±1% tolerance versus ±5%.
Understanding Tolerance
Tolerance tells you the range of actual resistance values you can expect from a resistor. A 10 kΩ resistor with ±5% tolerance could measure anywhere from:
For precision circuits, this 1,000 Ω spread is unacceptable. That is why op-amp feedback networks and voltage references use ±1% or ±0.1% resistors. The cost difference is modest: a ±1% metal-film resistor costs only slightly more than a ±5% carbon-film type.
The Classic Mnemonic
Generations of engineers have memorized the sequence "Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White" using various mnemonics. The traditional version begins "Bad Beer Rots Our Young Guts But Vodka Goes Well" — corresponding to digits 0 through 9. Use whatever memory aid works for you; the important thing is to internalize the order from 0 to 9.
Which End Is Which?
One of the most common mistakes is reading the resistor from the wrong end. Here are reliable ways to identify the reading direction:
- Tolerance band spacing: The tolerance band (gold, silver, or a narrow band) is spaced slightly farther from the other bands. Start reading from the opposite end.
- Band width: On some resistors, the tolerance band is noticeably narrower than the digit bands.
- No gold/silver as digits: Gold and silver never appear as significant digit bands. If you see gold or silver, that is the tolerance end — read from the other side.
- IEC 60062 marking: Some manufacturers print a wider gap before the tolerance band as a visual cue.
Common Mistakes
- Reading backwards: Always verify using the tolerance band position. Red-Red-Brown-Gold (220 Ω) read backwards would be Brown-Red-Red-Gold (1.2 kΩ) — a very different value.
- Confusing similar colors: Red and orange, blue and violet, and brown and red are commonly confused under poor lighting. Always verify under good illumination.
- Ignoring the multiplier: A Brown-Black-Red resistor is 1,000 Ω (1 kΩ), not 102 Ω. The third band is a multiplier, not a third digit.
- Forgetting sub-10Ω values: Resistors below 10 Ω use gold (×0.1) or silver (×0.01) multipliers. Blue-Grey-Gold-Gold = 6.8 Ω ±5%, not 680 MΩ.
Use our Resistor Color Code Calculator to instantly decode any 4-band or 5-band resistor by selecting the colors.