The standard common resistor values are not arbitrary; they are strictly defined by the IEC 60063 standard (Preferred numbers and preferred series for resistors and capacitors). This standard divides the logarithmic decade into specific series—most commonly E12, E24, and E96—based on the component's manufacturing tolerance. If you are designing a voltage divider, setting an op-amp gain, or biasing a transistor, you must select from these preferred numbers rather than calculating an arbitrary theoretical resistance.
The IEC 60063 Common Resistor Values Chart (E12, E24, E96)
How to read this table: The values below represent the base multiplier. To find your actual target resistance, multiply the base number by a decade (0.1, 1, 10, 100, 1k, 10k, 100k, 1M, etc.). For example, a base value of 4.7 yields 4.7Ω, 47Ω, 470Ω, 4.7kΩ, and 47kΩ. Which column applies to your installation? Use the E24 column for general-purpose 5% tolerance circuits (like pull-ups, LED current limiting, and basic biasing). Use the E96 column for 1% precision applications (like feedback networks, ADC dividers, and instrumentation). The E12 column is largely legacy, applying to older 10% carbon composition parts or high-power wirewound resistors where tight tolerance is unnecessary.
| Base Multiplier | E12 Series (±10%) | E24 Series (±5%) | E96 Series (±1%) |
|---|---|---|---|
| 1.0 | 1.0 | 1.0 | 1.00 |
| 1.1 | - | 1.1 | 1.10 |
| 1.2 | 1.2 | 1.2 | 1.21 |
| 1.3 | - | 1.3 | 1.33 |
| 1.5 | 1.5 | 1.5 | 1.47 |
| 1.6 | - | 1.6 | 1.58 |
| 1.8 | 1.8 | 1.8 | 1.74 |
| 2.0 | - | 2.0 | 1.91 |
| 2.2 | 2.2 | 2.2 | 2.15 |
| 2.4 | - | 2.4 | 2.40 |
| 2.7 | 2.7 | 2.7 | 2.67 |
| 3.0 | - | 3.0 | 3.01 |
| 3.3 | 3.3 | 3.3 | 3.32 |
| 3.6 | - | 3.6 | 3.65 |
| 3.9 | 3.9 | 3.9 | 3.92 |
| 4.3 | - | 4.3 | 4.32 |
| 4.7 | 4.7 | 4.7 | 4.75 |
| 5.1 | - | 5.1 | 5.11 |
| 5.6 | 5.6 | 5.6 | 5.62 |
| 6.2 | - | 6.2 | 6.19 |
| 6.8 | 6.8 | 6.8 | 6.81 |
| 7.5 | - | 7.5 | 7.50 |
| 8.2 | 8.2 | 8.2 | 8.25 |
| 9.1 | - | 9.1 | 9.09 |
Power Derating and Temperature Coefficient (TCR) Adjustments
A common mistake among hobbyists and junior engineers is assuming the nominal value from the chart above remains static on the PCB. In reality, environmental factors modify both the actual resistance and the safe power dissipation of the component. Understanding how derating rows and curves modify the base value is critical for reliable designs.
1. Temperature Coefficient of Resistance (TCR) Shifts
The chart gives you the nominal value at 20°C ambient. However, as the resistor self-heats from power dissipation or sits in a hot enclosure, its actual resistance shifts. This is governed by the TCR, measured in parts per million per degree Celsius (ppm/°C).
- Standard Thick Film (e.g., Yageo RC0603): Typically ±100 to ±200 ppm/°C.
- Precision Thin Film (e.g., Susumu RG series, Vishay TNPW): Typically ±10 to ±25 ppm/°C.
Worked Example: You place a standard 10kΩ (E96 base 1.00) thick-film resistor with a ±100 ppm/°C TCR in an enclosure that reaches 70°C ambient. The temperature rise (ΔT) from the 20°C baseline is 50°C.
Shift = 10,000Ω × (100 × 10⁻⁶) × 50°C = 50Ω.
Your actual resistance is now 10,050Ω. In a 12-bit ADC voltage divider, this 0.5% shift could introduce a 2-LSB measurement error. For precision analog front-ends, you must specify ±10 ppm/°C thin-film parts.
2. Ambient Power Derating
The power rating printed on the datasheet (e.g., 1/4W or 0.25W for a standard axial through-hole, or 0.1W for an 0603 SMD) is only valid up to a specific ambient temperature, usually 70°C. Above 70°C, the maximum allowable power derates linearly to zero at the maximum operating temperature (typically 155°C for standard thick film).
Worked Example: You are using a 0.25W resistor in a power supply enclosure that runs at 100°C ambient.
Derating slope = 0.25W / (155°C - 70°C) = 0.00294 W/°C.
Temperature above 70°C = 100°C - 70°C = 30°C.
Max Power = 0.25W - (30°C × 0.00294 W/°C) = 0.161W.
If your circuit dissipates 0.20W through this resistor, it will overheat and fail, despite being "under" the 0.25W nominal rating. Always check the manufacturer's power derating curve for high-ambient installations.
What This Chart Cannot Tell You (Parasitics and Limits)
While the IEC 60063 chart is the definitive guide for nominal resistance selection, it is purely a DC, low-frequency, room-temperature model. It completely omits three critical parameters that dictate real-world component selection, especially in RF, high-voltage, and high-speed digital circuits.
| Parameter | What It Is | Real-World Impact & Component Choice |
|---|---|---|
| Parasitic Inductance (ESL) | The inherent inductance created by the physical geometry of the resistive element and leads. | Wirewound resistors (even non-inductive types) have high ESL, making them useless above 10kHz. For high-frequency snubbers or RF termination, you must use thick/thin film SMD resistors (like 0402 or 0603 sizes) which have near-zero ESL. |
| Maximum Working Voltage | The absolute maximum voltage that can be applied across the resistor terminals, regardless of power rating. | A 10MΩ 0402 resistor rated for 0.0625W theoretically could handle 790V (P=V²/R). However, the physical gap between the 0402 pads limits the max working voltage to 50V. Exceeding this causes internal arcing, bypassing the power rating entirely. |
| Voltage Coefficient of Resistance (VCR) | The change in resistance value as the applied voltage increases. | High-value thick-film resistors (e.g., >1MΩ) can drop in value by 1% to 5% when subjected to high electric fields. For high-voltage divider networks, specify bulk metal foil or specialized high-voltage film resistors (e.g., Vishay VR series) with low VCR. |
When sourcing components for a new design, start with the IEC 60063 chart to lock in your nominal E24 or E96 base values. Then, immediately cross-reference your chosen physical package (e.g., 0805, 1206, or 1/2W axial) against the manufacturer's datasheet for maximum working voltage, TCR, and the 70°C derating knee. For further reading on component parasitics and standard values, refer to the SparkFun Resistor Tutorial or browse the application notes available on the Vishay Resistors portal. You can also review fundamental color code mappings and standard tables via All About Circuits.
