The colour code of resistor components is a standardized visual system that translates painted bands into resistance (ohms), multiplier, and tolerance. For a standard 4-band through-hole resistor, read the first two bands as significant digits, the third as the decimal multiplier, and the fourth as the tolerance percentage. For example, a resistor with Brown (1), Black (0), Red (×100), and Gold (±5%) bands equals 1,000 Ω (1 kΩ) with a guaranteed tolerance between 950 Ω and 1,050 Ω.
The Master Colour Code of Resistor Table (IEC 60062)
The globally recognized standard for component marking is IEC 60062. The table below covers 4-band, 5-band, and 6-band configurations. In a 5-band resistor, the first three bands are digits, the fourth is the multiplier, and the fifth is tolerance. A 6-band resistor adds a temperature coefficient (ppm/°C) as the final band.
| Colour | Digit (Bands 1, 2, 3) | Multiplier (Band 3 or 4) | Tolerance (Band 4 or 5) | Temp Coeff (Band 6) |
|---|---|---|---|---|
| Black | 0 | ×1 (10^0) | — | 250 ppm/°C |
| Brown | 1 | ×10 (10^1) | ±1% | 100 ppm/°C |
| Red | 2 | ×100 (10^2) | ±2% | 50 ppm/°C |
| Orange | 3 | ×1k (10^3) | — | 15 ppm/°C |
| Yellow | 4 | ×10k (10^4) | — | 25 ppm/°C |
| Green | 5 | ×100k (10^5) | ±0.5% | 20 ppm/°C |
| Blue | 6 | ×1M (10^6) | ±0.25% | 10 ppm/°C |
| Violet | 7 | ×10M (10^7) | ±0.1% | 5 ppm/°C |
| Grey | 8 | ×100M (10^8) | ±0.05% | 1 ppm/°C |
| White | 9 | ×1G (10^9) | — | — |
| Gold | — | ×0.1 (10^-1) | ±5% | — |
| Silver | — | ×0.01 (10^-2) | ±10% | — |
Worked 5-Band Example: Orange (3), Orange (3), Black (0), Brown (×10), Brown (±1%). Calculation: 330 × 10 = 3,300 Ω (3.3 kΩ) with a 1% tolerance.
Rows People Get Wrong (And How to Avoid Them)
Even experienced technicians misread bands under poor lighting or when dealing with non-standard manufacturing batches. Here are the most common bench-level errors:
- Red vs. Orange in Faded Lighting: Under warm 3000K-5000K LED bench lamps, red (2) and orange (3) look nearly identical. Fix: Use a 6500K daylight-calibrated desk lamp, or keep a known 220 Ω (Red-Red-Brown) and 330 Ω (Orange-Orange-Brown) reference resistor on your bench for direct visual comparison.
- Gold and Silver as Multipliers: Beginners often assume gold and silver only denote tolerance. If gold or silver appears in the multiplier position (third band on a 4-band resistor), it denotes a decimal fraction. A Green-Blue-Gold-Gold resistor is 5.6 × 0.1 = 0.56 Ω, not 5.6 GΩ.
- Reading Direction on 5-Band Resistors: If a 5-band resistor has a brown band on both ends, determining the starting side is difficult. Rule: The tolerance band (usually brown for 1% or red for 2%) is often spaced slightly wider from the multiplier band. If spacing is identical, check if reading it backward results in a non-standard E24/E96 value. Standard values almost always dictate the correct orientation.
- Confusing the 6th Band: On 6-band resistors, the final band is the temperature coefficient (ppm/°C), not an extra digit. Reading it as a digit will yield mathematically impossible resistance values.
Standard Variants: IEC 60062 vs. Legacy MIL-SPEC and BS 1852
While IEC 60062 is the modern global baseline, you will encounter legacy and specialized standards when repairing older equipment or working with military-grade hardware.
- IEC 60062 (Global Modern): The standard detailed in the table above. Used for virtually all commercial through-hole carbon film and metal film resistors manufactured after 1990.
- US MIL-SPEC (MIL-PRF-39008): Used in aerospace and military applications. These 5-band or 6-band resistors use the standard IEC color code for the first four bands, but add a 5th or 6th band to indicate failure rate rather than temperature coefficient. For example, a 5th band of 'M' indicates a 1% failure rate per 1,000 hours, and 'P' indicates 0.1%.
- Old UK BS 1852 (Letter Coding): Before color bands became universally dominant on all form factors, British Standard BS 1852 used printed alphanumeric codes. You will still see this on old UK schematics and some surface-mount adapters. 'R' stands for ohms, 'K' for kilo-ohms, and 'M' for mega-ohms. The letter replaces the decimal point. Example:
4K7= 4.7 kΩ;R22= 0.22 Ω.
Do not confuse IEC 60062 component color codes with IEC 60446 / NEC AC mains wire colors. In modern AC wiring, Brown indicates a Live (Phase) conductor carrying lethal voltage. In the resistor colour code, Brown simply represents the digit 1. Never use component color logic to trace mains wiring, and never use wire color logic to read a circuit board.
Decision Tree: Identifying Faded, Missing, or Ambiguous Bands
When a resistor is heat-damaged, chemically washed, or simply too small to read, use this decision path to determine its value and select a concrete replacement.
| Symptom / Condition | Diagnostic Action | Concrete Resolution / Replacement Pick |
|---|---|---|
| Bands are clear, but direction is ambiguous. | Measure with DMM out-of-circuit. Match reading to nearest E24/E96 standard value. | Keep original. Verify circuit function. |
| 3rd or 4th band is burnt/missing, but first two are legible. | Desolder one leg. Measure. If open (OL), the multiplier is lost. | Trace schematic. If unknown, assume ×100 (Red) for general signal paths. |
| Resistor is completely charred/illegible (Power Supply). | Do NOT guess. A burnt PSU resistor usually indicates a shorted downstream MOSFET or diode. | Replace with Vishay MRS25000C series (0.6W, 1%, 50ppm) metal film. Must fix root cause first. |
| Resistor is completely charred/illegible (Logic/Microcontroller board). | Identify pin function. If connected to GPIO/I2C, it is a pull-up/pull-down. | Replace with Yageo MFR-25FRF52-10K (10kΩ, 1%, 0.25W). 10kΩ is the universal I2C/GPIO default. |
| Resistor is in series with a standard LED on a 5V rail. | Calculate required current limiting. (5V - 2V LED drop) / 15mA = 200Ω. | Replace with Yageo MFR-25FRF52-220R (220Ω, 1%, 0.25W). 220Ω is the standard 5V LED safe limit. |
For a comprehensive, high-reliability bench stock that covers 95% of repair scenarios, purchase the Vishay MRS16 / MRS25 E24/E96 kit. These 1% metal film resistors offer 50ppm/°C stability, vastly outperforming the cheap 5% carbon film assortments that drift under thermal load.
Practical Verification: When to Trust the Bands vs. the Multimeter
The colour code of resistor bands tells you the nominal value at the factory. It does not tell you the current state of the component after years of thermal cycling. Always verify critical resistors with a digital multimeter (DMM), but follow these strict measurement protocols to avoid false readings:
- Never Measure In-Circuit: Measuring a resistor while it is still soldered to a PCB will yield the equivalent resistance of the entire parallel network connected to those nodes. The reading will almost always be lower than the actual resistor value. You must desolder at least one leg of the resistor to lift it off the pad before measuring.
- Null Your Test Leads: Standard DMM leads have an inherent resistance of 0.1 Ω to 0.4 Ω. When measuring low-value resistors (e.g., a 0.56 Ω current-sense resistor in a power supply), short the probe tips together, note the lead resistance, and subtract it from your final measurement. Better yet, use a DMM with a relative (REL) mode to auto-zero the leads.
- Check for Thermal Drift: If a resistor measures correctly when cold but drifts significantly when hit with freeze-spray or a heat gun, its temperature coefficient has degraded. Replace it with a 1% or 0.1% precision metal film resistor to restore circuit stability.
By combining the IEC 60062 visual standard with rigorous out-of-circuit DMM verification, you eliminate guesswork and ensure your repairs and builds operate exactly as engineered.
