To calculate resistance by colour code, you decode the painted bands using the globally recognized IEC 60062 standard. There is no regional variation for through-hole resistor bands; a brown-black-red-gold resistor reads as 1kΩ whether you are in London, Tokyo, or Chicago. Below is the master reference chart to decode any 4-band or 5-band component on your bench.
The IEC 60062 Resistor Colour Code Reference Table
Read this table left-to-right for 4-band resistors (Digit 1, Digit 2, Multiplier, Tolerance). For 5-band precision resistors (1% or better), read Digit 1, Digit 2, Digit 3, Multiplier, Tolerance.
| Colour | Significant Digit (1st/2nd/3rd Band) | Multiplier (Value × 10^n) | Tolerance (Final Band) | Temp. Coeff. (6th Band) |
|---|---|---|---|---|
| Black | 0 | ×1 (10^0) | — | 250 ppm/°C |
| Brown | 1 | ×10 (10^1) | ±1% (F) | 100 ppm/°C |
| Red | 2 | ×100 (10^2) | ±2% (G) | 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% (D) | — |
| Blue | 6 | ×1M (10^6) | ±0.25% (C) | 10 ppm/°C |
| Violet | 7 | ×10M (10^7) | ±0.1% (B) | 5 ppm/°C |
| Grey | 8 | — | ±0.05% (A) | — |
| White | 9 | — | — | — |
| Gold | — | ×0.1 (10^-1) | ±5% (J) | — |
| Silver | — | ×0.01 (10^-2) | ±10% (K) | — |
Rows and Bands People Get Wrong
Even experienced makers misread specific edge cases on the IEC 60062 chart. Watch for these common traps:
When black appears as the multiplier band (the third band on a 4-band resistor), it means 10^0, which equals 1. A brown-black-black-gold resistor is 10 × 1 = 10Ω, not 0Ω. (A true 0Ω jumper resistor typically has a single black band in the center of the body).
- Gold and Silver Multipliers: These are used for values under 10Ω. A red-red-gold-gold resistor is 22 × 0.1 = 2.2Ω (±5%). A green-blue-silver-gold is 56 × 0.01 = 0.56Ω.
- Reading Direction: Always start from the end closest to a band. The tolerance band (usually gold or silver) is often spaced slightly further apart from the significant digits. If spacing is ambiguous, look for the tolerance color: gold and silver are never used as significant digits, so they must be the final band.
- Temperature Coefficient (6th Band): Found only on high-precision 5-band resistors. A brown 6th band means 100 ppm/°C. This tells you how much the resistance drifts per degree Celsius of temperature change, critical for precision analog front-ends and current shunts.
Standard Variants: Component Codes vs. Wiring Codes
A critical bench hazard occurs when makers confuse IEC 60062 component bands with regional mains wiring codes. While resistor bands are universally IEC 60062, wire insulation colors vary wildly by region.
| Colour | IEC 60062 (Resistors - Global) | IEC 60446 (EU/UK/AU Wiring) | NEC (US/Canada Wiring) | Old UK BS 7671 (Pre-2004) |
|---|---|---|---|---|
| Green / Yellow | 5 / 4 (Digits) | Protective Earth (Ground) | Equipment Ground | Protective Earth |
| Brown | 1 (Digit) / ±1% (Tol) | Line (Live / Hot) | Hot (in some 277/480V) | Line (Live) |
| Blue | 6 (Digit) / ±0.25% (Tol) | Neutral | Neutral (in DC systems) | Neutral |
| Black | 0 (Digit) / ×1 (Mult) | Line (Phase 2 in 3-phase) | Hot (120V/240V Standard) | Neutral (Old 2-wire) |
Decision Path: Faded, Missing, or Ambiguous Markings
Never guess a resistor value if the paint is degraded, burnt, or ambiguous. Guessing a bias resistor value in a tube amplifier or a current-limiting resistor in an LED driver can result in catastrophic component failure. Use this decision tree to determine your next step.
| Symptom / Condition | Action Required | Final Tool / Concrete Pick |
|---|---|---|
| Bands are crisp, intact, and spaced clearly | Read visually using the IEC 60062 chart above. | Visual decode (No tool needed) |
| Bands are faded, scratched, or ambiguous | Desolder one leg to isolate from the circuit, then measure. | Digital Multimeter (e.g., Fluke 117) on lowest Ω range |
| Resistor is soldered in-circuit and you cannot desolder | Measure in-circuit, but only accept the reading if it matches a standard E24/E96 value. If it reads lower, parallel paths are skewing the result. | DMM (Note: In-circuit reading is a maximum bound) |
| Body is blistered, blackened, or smells burnt | Do not measure. The carbon film or metal oxide layer has likely fractured or carbonized, altering the value permanently. | Discard and replace (Check schematic for original value) |
Worked Calculation and Bench Verification
Let's run through two concrete examples to solidify the math, followed by the correct bench procedure for verifying them with a multimeter.
Example 1: 4-Band Standard Tolerance
Bands: Yellow - Violet - Orange - Gold
- Digit 1 (Yellow): 4
- Digit 2 (Violet): 7
- Multiplier (Orange): ×1,000 (10^3)
- Tolerance (Gold): ±5%
- Calculation: 47 × 1,000 = 47,000Ω = 47kΩ.
- Acceptable Range: 44.65kΩ to 49.35kΩ.
Example 2: 5-Band Precision
Bands: Red - Red - Black - Brown - Brown
- Digit 1 (Red): 2
- Digit 2 (Red): 2
- Digit 3 (Black): 0
- Multiplier (Brown): ×10 (10^1)
- Tolerance (Brown): ±1%
- Calculation: 220 × 10 = 2,200Ω = 2.2kΩ.
- Acceptable Range: 2.178kΩ to 2.222kΩ.
Bench Verification Protocol
When verifying these values on the bench with a digital multimeter, follow this sequence to ensure accuracy:
- Zero the leads: Touch the probes together. Note the lead resistance (usually 0.1Ω to 0.3Ω). Subtract this from your final reading if measuring resistors under 10Ω.
- Isolate the component: If measuring in-circuit, ensure all power is off and large capacitors are discharged. Be aware that semiconductor junctions and parallel resistors will yield a falsely low reading.
- Select the correct range: If your DMM is not auto-ranging, select the range just above the expected value (e.g., use the 20kΩ range for a 4.7kΩ resistor) to maximize ADC resolution.
- Avoid skin contact: Do not pinch the metal probe tips and the resistor leads with your bare fingers simultaneously. Your body's resistance (typically 10kΩ to 100kΩ depending on skin moisture) will form a parallel circuit, skewing high-value resistor measurements.
For a comprehensive interactive breakdown of edge cases and SMD codes, the All About Circuits resistor calculator remains an excellent bench reference to cross-check your manual IEC 60062 math before soldering.
