A three band resistor color code uses the first two bands for significant digits and the third band for the decimal multiplier. Because there is no fourth band, the default tolerance is universally assumed to be ±20%. To read it, orient the resistor so the bands are grouped to the left, read the first two colors as numbers, and append the zeros indicated by the third color.
The Complete Three Band Resistor Color Code Table
The following chart maps directly to the IEC 60062 standard. Keep this bookmarked on your bench for quick reference when sorting through mixed component bins.
| Band Color | 1st Band (Digit 1) | 2nd Band (Digit 2) | 3rd Band (Multiplier) | Example Value (3-Band) |
|---|---|---|---|---|
| Black | 0 | 0 | ×1 (10⁰) | — (Not used as 1st band) |
| Brown | 1 | 1 | ×10 (10¹) | 11 × 10 = 110 Ω |
| Red | 2 | 2 | ×100 (10²) | 22 × 100 = 2.2 kΩ |
| Orange | 3 | 3 | ×1,000 (10³) | 33 × 1k = 33 kΩ |
| Yellow | 4 | 4 | ×10,000 (10⁴) | 44 × 10k = 440 kΩ |
| Green | 5 | 5 | ×100,000 (10⁵) | 55 × 100k = 5.5 MΩ |
| Blue | 6 | 6 | ×1,000,000 (10⁶) | 66 × 1M = 66 MΩ |
| Violet | 7 | 7 | ×10,000,000 (10⁷) | 77 × 10M = 770 MΩ |
| Gray | 8 | 8 | ×100,000,000 (10⁸) | 88 × 100M = 8.8 GΩ |
| White | 9 | 9 | ×1,000,000,000 (10⁹) | 99 × 1G = 99 GΩ |
Source reference: Standard values align with the All About Circuits color code guide and IEC 60062 specifications.
Standard Variants: IEC 60062 vs. Historical Systems
When dealing with house wiring, you have to navigate the frustrating split between US NEC (black=hot, white=neutral, bare=ground) and IEC 60446 / old UK standards (brown=live, blue=neutral, green/yellow=earth). Fortunately, electronic component color codes do not suffer from this regional fragmentation.
The modern three band resistor color code is universally governed by IEC 60062. Whether you buy a carbon film resistor from Vishay in the US, Yageo in Asia, or a generic kit from eBay, the IEC standard applies globally. There is no "US version" versus "EU version" of a resistor color code.
The Pre-1950s Body-Tip-Dot Variant
If you are restoring antique tube radios or vintage test equipment, you might encounter the old US MIL-SPEC or UK "body-tip-dot" system. In this obsolete variant, the color of the resistor's physical body was the first digit, the painted tip was the second digit, and a single dot in the middle was the multiplier. For example, a brown-bodied resistor with a red tip and a yellow dot meant 12 × 10,000 = 120 kΩ. If you apply the modern IEC 60062 three-band logic to these vintage parts, you will misread them entirely. Always check the manufacturing era if the component lacks distinct, evenly spaced painted bands.
Rows and Colors People Get Wrong on the Bench
Even experienced technicians misread resistors under poor lighting or when dealing with cheap manufacturing tolerances. Here are the specific failure modes to watch for:
- Brown (1) vs. Red (2): This is the most common error. Carbon film resistor bodies are naturally dark brown. A red band (2) can easily blend into the body, making a 220 Ω resistor (red-red-brown) look like a 120 Ω resistor (brown-red-brown). Fix: Tilt the resistor under a cool-white LED bench lamp; red will reflect distinctly, while brown will absorb the light.
- Orange (3) vs. Yellow (4): UV exposure and heat from nearby components can sun-fade yellow bands into a pale orange. If a yellow band looks slightly burnt or washed out, do not trust your eyes.
- Violet (7) vs. Blue (6): In low light, dark blue bands often read as black or violet. A 68 Ω resistor (blue-gray-black) can easily be misread as 78 Ω (violet-gray-black) if the blue band lacks proper illumination.
- Phantom Gold/Silver Bands: Beginners often look for gold or silver on a 3-band resistor. Under IEC 60062, gold and silver are strictly reserved for tolerance bands (the 4th or 5th band) and are never valid for the first three digits. If you see a gold band, you are holding a 4-band or 5-band resistor and are miscounting your significant digits.
If a resistor's bands are charred, completely faded, or obscured by conformal coating, do not guess. Guessing a bias resistor value in a transistor circuit can lead to thermal runaway. Desolder one leg of the resistor to isolate it from parallel circuit paths, and measure it directly with a digital multimeter (DMM) in ohms mode. If the DMM reads open (OL) or wildly outside the expected schematic value, the internal carbon track has fractured; discard it and replace it with a fresh 1% metal film equivalent.
Frequently Asked Questions (FAQ)
Why does a three band resistor color code lack a tolerance stripe?
The three-band format is an older, cost-saving manufacturing standard. Because it lacks a fourth band to specify precision, the electronics industry universally defaults to a ±20% tolerance for three-band resistors. This means a 100 Ω three-band resistor (brown-black-brown) could legally measure anywhere between 80 Ω and 120 Ω straight out of the factory. Today, ±20% is generally unacceptable for modern precision logic or analog audio, which is why 4-band (±5% or ±1%) and 5-band (±1% or ±0.1%) resistors have largely replaced them in modern PCB assembly.
How do I read a three band resistor when the paint is faded or burnt?
When visual inspection fails, you must rely on electrical measurement. First, power down the circuit and discharge any large capacitors. Next, use a soldering iron to lift one leg of the resistor from the PCB pad. This is a critical step: if you measure a resistor while it is still soldered into the board, the multimeter will measure the equivalent resistance of the entire parallel circuit, giving you a falsely low reading. Once isolated, touch your DMM probes to the leads. If the reading is stable and matches a standard E12/E24 value, trust the meter over your eyes. If the resistor body is physically charred black, the carbon composition has likely altered; throw it away and consult the schematic or service manual for the original design value.
Can I use a 4-band resistor in place of a 3-band resistor?
Yes, absolutely. A 4-band resistor is a direct, higher-precision upgrade. If your schematic calls for a 3-band 470 Ω resistor (yellow-violet-brown), you can safely substitute a 4-band 470 Ω resistor (yellow-violet-brown-gold). The first three bands will be identical, and the fourth band (gold for ±5% or brown for ±1%) simply guarantees a tighter manufacturing tolerance than the ±20% default of the 3-band part. In fact, upgrading from 3-band carbon composition to 4-band or 5-band metal film resistors is a standard practice when restoring vintage audio amplifiers to reduce thermal noise and improve long-term stability. For further reading on component substitution, refer to Vishay's official resistor color code and specification documentation.
