Resistor Color Code: How to Read Any Resistor
Resistors are too small to print numbers on, so manufacturers encode their values as colored stripes. The color code dates to the 1920s, when the Radio Manufacturers Association standardized it. Once you know the system, reading a resistor takes about two seconds.
The Color Code Table
| Color | Digit | Multiplier | Tolerance | Temp coeff (ppm/°C) |
|---|---|---|---|---|
| Black | 0 | ×1 | — | 250 |
| Brown | 1 | ×10 | ±1% | 100 |
| Red | 2 | ×100 | ±2% | 50 |
| Orange | 3 | ×1,000 | — | 15 |
| Yellow | 4 | ×10,000 | — | 25 |
| Green | 5 | ×100,000 | ±0.5% | 20 |
| Blue | 6 | ×1,000,000 | ±0.25% | 10 |
| Violet | 7 | ×10,000,000 | ±0.1% | 5 |
| Gray | 8 | ×100,000,000 | ±0.05% | 1 |
| White | 9 | — | — | — |
| Gold | — | ×0.1 | ±5% | — |
| Silver | — | ×0.01 | ±10% | — |
| None | — | — | ±20% | — |
The Mnemonic
In order from 0 to 9: Better Be Right Or Your Great Big Venture Goes Wrong
Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White
Reading a 4-Band Resistor
The standard 4-band resistor has:
- Band 1: first digit
- Band 2: second digit
- Band 3: multiplier
- Band 4: tolerance (usually separated by a gap from the first three)
Example: Brown, Black, Red, Gold
Band 1 (Brown) = 1 | Band 2 (Black) = 0 | Band 3 (Red) = ×100 | Band 4 (Gold) = ±5%
Value: 10 × 100 = 1,000 Ω = 1 kΩ ±5%
Example: Yellow, Violet, Orange, Gold
4 | 7 | ×1,000 | ±5% = 47,000 Ω = 47 kΩ ±5%
Reading a 5-Band Resistor
Precision resistors (1% tolerance and better) use 5 bands for one extra significant digit:
- Bands 1–3: three digits
- Band 4: multiplier
- Band 5: tolerance
Example: Red, Red, Black, Black, Brown
2 | 2 | 0 | ×1 | ±1% = 220 Ω ±1%
5-band resistors can look deceptively like 4-band ones if the gap between the value bands and tolerance band isn't obvious. The tolerance band tells you: if it's Brown (±1%), Red (±2%), Green (±0.5%), Blue (±0.25%), or Violet (±0.1%), you're reading a 5-band resistor. If it's Gold (±5%) or Silver (±10%), it's 4-band.
Tolerance: What the Range Means
A 100 Ω ±5% resistor may measure anywhere from 95 Ω to 105 Ω. For most circuits this is fine. For precision applications — op-amp circuits, filters, voltage dividers with tight requirements — use 1% or better.
| Tolerance | 100Ω range | 10kΩ range | Typical use |
|---|---|---|---|
| ±20% (none) | 80–120 Ω | 8k–12kΩ | Non-critical circuits |
| ±10% (silver) | 90–110 Ω | 9k–11kΩ | General purpose |
| ±5% (gold) | 95–105 Ω | 9.5k–10.5kΩ | Most hobbyist work |
| ±1% (brown) | 99–101 Ω | 9.9k–10.1kΩ | Precision circuits |
| ±0.1% (violet) | 99.9–100.1 Ω | 9.99k–10.01kΩ | Measurement circuits |
Which Way Do You Read It?
Hold the resistor so the tolerance band (gold or silver) faces right. Read left to right. If there's no gold or silver band (±20%), look for the gap — it's usually between the third and fourth bands. If you genuinely can't tell, measure it with a multimeter.
Frequently Asked Questions
How do I tell the difference between a 4-band and 5-band resistor?
Look at the tolerance band (the last band, usually separated by a gap). If it's Brown (±1%), Red (±2%), Green (±0.5%), Blue (±0.25%), or Violet (±0.1%), it's a 5-band resistor with three significant digits. If it's Gold (±5%) or Silver (±10%), it's a standard 4-band resistor. You can also count the bands, but the tolerance color is the quickest identifier.
What does the ±5% on a resistor actually mean?
The tolerance tells you the acceptable range of error from the marked value. A 100 Ω ±5% resistor might actually measure anywhere from 95 Ω to 105 Ω and still be within spec. For most hobbyist circuits this is fine, but precision applications like op-amp circuits or filters need tighter tolerances—look for ±1% (Brown band) or better.
I have a resistor with no gold or silver band—how do I know which direction to read it?
Resistors with no tolerance band (±20% tolerance) are harder to orient. Look for any visual break or the band that appears slightly separated from the others—that's your tolerance band and should face right. If you still can't tell, try reading it both ways and see which value seems more likely for your circuit, or use an ohmmeter to verify the actual resistance.
What's the difference between a 1 kΩ resistor marked as Brown-Black-Red versus Brown-Black-Black-Brown?
Brown-Black-Red is a 4-band resistor: 1-0-×100 = 1,000 Ω (1 kΩ) with ±5% tolerance. Brown-Black-Black-Brown is a 5-band resistor: 1-0-0-×1 = 100 Ω with ±1% tolerance. These are completely different values—the 5-band has three digits (100) while the 4-band has two (10), so always count the bands before reading.
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