When you are digging through a mixed bin of 1/4W carbon films or trying to read the microscopic printing on an 0402 surface-mount device, guessing is not an option. The resistor code chart translates physical markings into exact ohmic values, tolerance limits, and thermal stability metrics. For through-hole components, these markings follow the IEC 60062 standard. For surface-mount devices (SMD), the industry relies on 3-digit, 4-digit, or EIA-96 alphanumeric systems.
Below is the complete, bench-ready reference data you need to identify any resistor, calculate its thermal derating, and understand the physical limitations the chart leaves out.
The Master Resistor Color Code Chart (IEC 60062)
How to read this table: Hold the resistor so the tolerance band (usually gold or silver) is on the far right. Read the bands from left to right. Band 1 and Band 2 (and Band 3 on 5-band resistors) provide the significant digits. The Multiplier column tells you how many zeros to append (or the decimal shift for gold/silver). The Tolerance column defines the manufacturing variance (e.g., ±5%). The TCR column (Band 5 or 6) defines the Temperature Coefficient of Resistance in parts per million per degree Celsius (ppm/°C).
| Color | Band 1 & 2 (Digit) | Band 3 (Multiplier) | Band 4 (Tolerance) | Band 5/6 (TCR ppm/°C) |
|---|---|---|---|---|
| Black | 0 | ×1 (10⁰) | — | 250 |
| Brown | 1 | ×10 (10¹) | ±1% (F) | 100 |
| Red | 2 | ×100 (10²) | ±2% (G) | 50 |
| Orange | 3 | ×1k (10³) | — | 15 |
| Yellow | 4 | ×10k (10⁴) | — | 25 |
| Green | 5 | ×100k (10⁵) | ±0.5% (D) | — |
| Blue | 6 | ×1M (10⁶) | ±0.25% (C) | 10 |
| Violet | 7 | ×10M (10⁷) | ±0.1% (B) | 5 |
| Gray | 8 | — | ±0.05% (A) | — |
| White | 9 | — | — | — |
| Gold | — | ×0.1 (10⁻¹) | ±5% (J) | — |
| Silver | — | ×0.01 (10⁻²) | ±10% (K) | — |
- 10 kΩ (5%): Brown, Black, Orange, Gold
- 4.7 kΩ (5%): Yellow, Violet, Red, Gold
- 220 Ω (5%): Red, Red, Brown, Gold
- 100 Ω (1%): Brown, Black, Black, Brown, Brown
- 330 kΩ (5%): Orange, Orange, Yellow, Gold
SMD Resistor Codes and the EIA-96 Standard
Surface-mount resistors lack the physical real estate for color bands. Instead, they use printed numeric codes. For standard 5% tolerance parts (usually 0805 size and larger), a 3-digit code is used: the first two digits are significant, and the third is the multiplier (e.g., 103 = 10 × 10³ = 10 kΩ). For 1% tolerance parts, a 4-digit code is used: the first three digits are significant, and the fourth is the multiplier (e.g., 1002 = 100 × 10² = 10 kΩ).
When components shrink to 0603 and 0402 sizes, there is no room for four digits. The industry adopted the EIA-96 standard, which uses a 3-character alphanumeric code. The first two digits represent a base value lookup (from 01 to 96), and the final letter is a multiplier.
| Letter Code | Multiplier Value | Scientific Notation | Example (Base Code 01 = 100) |
|---|---|---|---|
| Z | 0.001 | 10⁻³ | 0.1 Ω |
| Y or R | 0.01 | 10⁻² | 1 Ω |
| X or S | 0.1 | 10⁻¹ | 10 Ω |
| A | 1 | 10⁰ | 100 Ω |
| B or H | 10 | 10¹ | 1 kΩ |
| C | 100 | 10² | 10 kΩ |
| D | 1,000 | 10³ | 100 kΩ |
| E | 10,000 | 10⁴ | 1 MΩ |
| F | 100,000 | 10⁵ | 10 MΩ |
Note: If you encounter an SMD resistor marked with a single 0 or 000, it is a zero-ohm jumper, used for routing traces on single-layer PCBs or as a configurable link.
Temperature Coefficient (TCR) and Thermal Derating
A common question when reading spec sheets is: which column applies to the reader's installation? If you are building a general-purpose 5V digital logic pull-up or an LED current limiter, you only need the Digit, Multiplier, and Tolerance columns. However, if your circuit is a precision analog front-end, an RTD measurement bridge, or operates in an enclosure where ambient temperatures exceed 40°C, the TCR column (Band 5 or 6) becomes the most critical column in the chart.
How derating rows modify the base value: Unlike wire ampacity tables where derating reduces the allowable current limit, resistor TCR derating modifies the actual physical resistance of the component as it heats up. The TCR value (e.g., 100 ppm/°C) acts as a thermal drift modifier. The formula to calculate the shifted resistance is:
Ractual = Rnominal × [1 + (TCR × ΔT)]
Where ΔT is the temperature rise above the standard 25°C baseline.
Worked Numeric Example: You have a 10 kΩ precision resistor with a Red TCR band (50 ppm/°C). It is mounted near a voltage regulator and reaches 75°C during operation.
ΔT = 75°C - 25°C = 50°C.
Drift = 10,000 Ω × (50 × 10⁻⁶) × 50 = 25 Ω.
Your 10,000 Ω resistor is now operating at 10,025 Ω. In a 12-bit ADC reference circuit, a 25 Ω shift on a voltage divider can easily introduce a 2-3 LSB (Least Significant Bit) error, ruining your measurement accuracy.
What the Chart Cannot Tell You (and How to Verify)
The IEC 60062 color chart and EIA-96 tables are strictly for identifying nominal resistance and tolerance. They are blind to several critical physical parameters that dictate whether a part will survive your specific application.
- Power Rating (Wattage): A 10 kΩ color code looks identical on a 1/8W axial resistor and a 2W power resistor. You must verify the physical footprint. For SMD, an 0402 package is typically 1/16W (62.5mW), an 0603 is 1/10W (100mW), and an 0805 is 1/8W (125mW). Always calculate I²R losses to ensure you are operating below 50% of the rated wattage for long-term reliability.
- Maximum Working Voltage: High-value resistors (e.g., 10 MΩ) used in mains-voltage snubber circuits or high-impedance dividers can suffer internal arcing. A standard 1/4W axial resistor typically has a max working voltage limit of 250V, regardless of what Ohm's Law suggests it could theoretically handle.
- Parasitic Inductance and Capacitance: The code chart does not reveal the internal construction. A wirewound 10 Ω power resistor will have significant parasitic inductance, making it useless as a snubber or high-frequency RF load. For RF and high-speed digital termination, you must specifically source thin-film or thick-film chip resistors, which are inherently non-inductive.
- Pulse Withstand Capability: Standard thick-film SMD resistors will crack or burn open under high-energy transient pulses (like ESD or inductive kickback). If your circuit faces transients, you must look for specialized "pulse-withstand" or "surge-rated" resistors, which use specialized carbon composition or metal glaze elements not identifiable by the standard color code.
Keep this chart bookmarked at your bench, but always cross-reference the physical dimensions and the manufacturer's specific datasheet for voltage, power, and thermal limits before finalizing your BOM.
