What is a resistor color code calculator?
Most through-hole resistors do not print their resistance value as text. Instead, they use a standardized series of colored bands to represent digits, multipliers, and tolerance. A resistor color code calculator helps you quickly interpret these colors and convert them into:
- Nominal resistance value (Ω, kΩ, or MΩ)
- Multiplier (power of ten)
- Tolerance (accuracy of the resistor)
- Temperature coefficient (for 6-band resistors)
This is especially useful when troubleshooting equipment, replacing components on control boards, or validating legacy designs where silk-screen information may be missing.
The resistor color code system
While 4-band resistors are the most common in general electronics, precision resistors often use 5 or 6 bands. The number of bands determines how many digits are encoded.
| Type | Bands | Meaning | Typical use |
|---|---|---|---|
| 4-band | Digit 1, Digit 2, Multiplier, Tolerance | Standard resistor identification | General-purpose designs |
| 5-band | Digit 1, Digit 2, Digit 3, Multiplier, Tolerance | Higher precision, three-digit resolution | Measurement circuits, industrial controls |
| 6-band | Digit 1, Digit 2, Digit 3, Multiplier, Tolerance, Tempco | Encodes temperature coefficient (ppm/°C) | Precision instrumentation |
Standard resistor color code reference
The following table shows the standard IEC color mapping for digits and multipliers:
| Color | Digit | Multiplier | Tolerance | Tempco (ppm/°C) |
|---|---|---|---|---|
| Black | 0 | × 100 | – | – |
| Brown | 1 | × 101 | ±1% | 100 |
| Red | 2 | × 102 | ±2% | 50 |
| Orange | 3 | × 103 | – | 15 |
| Yellow | 4 | × 104 | – | 25 |
| Green | 5 | × 105 | ±0.5% | – |
| Blue | 6 | × 106 | ±0.25% | 10 |
| Violet | 7 | × 107 | ±0.1% | 5 |
| Gray | 8 | × 108 | ±0.05% | 1 |
| White | 9 | × 109 | – | – |
| Gold | – | × 10-1 | ±5% | – |
| Silver | – | × 10-2 | ±10% | – |
How to identify resistor orientation
Many resistors are symmetrical and it can be difficult to see which side is “first.” A common rule is:
- The tolerance band (gold, silver, brown, red) is usually spaced slightly apart from the other bands.
- Start reading the resistor from the opposite end of the tolerance band.
- If the orientation is unclear, the calculator's visual preview helps you compare patterns.
Design considerations when selecting resistors
- Power rating matters: The color code does not indicate wattage. Always match the resistor’s power rating (e.g., 1/8 W, 1/4 W) to your circuit’s needs.
- Temperature effects: Precision circuits benefit from low-tempco resistors such as metal film types.
- Check preferred value series: E6, E12, E24 and E96 series determine what exact values are available. Not all calculated values exist in real products.
- Age and heat discoloration: Old or overheated resistors may fade in color. When unsure, confirm with a multimeter.
This calculator accelerates troubleshooting and design work by providing fast, accurate decoding of resistor color bands—ideal for field service, lab use, or repairing industrial control equipment.
