The standard resistance values table is defined internationally by the IEC 60063 standard (historically known in the US as EIA RS-279). It dictates the specific base ohmic values manufacturers are permitted to produce. If you need a 5% tolerance resistor, you must select from the 24 base values of the E24 series. If you need 1% precision, you select from the 96 base values of the E96 series. These base numbers are then scaled by decade multipliers (×10n) to cover everything from 0.1Ω to 10MΩ.
How to Read the IEC 60063 Standard Resistance Table
Unlike wire ampacity charts that use complex derating rows for temperature and bundling, the standard resistance table relies on logarithmic spacing and tolerance mapping. The core rule is simple: the tolerance of the component dictates which series column applies to your installation.
- E12 Series (12 values): Used for 10% and 20% tolerances. Common in older carbon composition resistors or high-voltage specialty parts.
- E24 Series (24 values): The universal standard for 5% tolerance thick-film and carbon film resistors. If you are buying standard through-hole or 0805 SMD resistors, you are buying E24.
- E96 Series (96 values): The standard for 1% tolerance thin-film and precision thick-film resistors.
- E192 Series (192 values): Used for 0.5%, 0.25%, and 0.1% ultra-precision metrology resistors.
Complete E-Series Base Values (E12, E24, E96)
Below is the complete, unabbreviated data table for the most commonly sourced base values. To find your exact resistor, take the base value and apply the decade multiplier (e.g., base 47 × 103 = 47kΩ).
| Series (Tolerance) | Base Values (First Two/Three Significant Digits) |
|---|---|
| E12 (10% / 20%) | 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 |
| E24 (5%) | 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91 |
E96 Series (1%) Complete Base Values
The E96 series contains 96 base values. Because 1% resistors are the modern default for precision analog front-ends, ADC voltage dividers, and feedback loops, this complete list is bookmark-friendly for quick bench lookups.
| Step 1-24 | Step 25-48 | Step 49-72 | Step 73-96 |
|---|---|---|---|
| 100 | 174 | 294 | 487 |
| 102 | 178 | 301 | 499 |
| 105 | 182 | 309 | 511 |
| 107 | 187 | 316 | 523 |
| 110 | 191 | 324 | 536 |
| 113 | 196 | 332 | 549 |
| 115 | 200 | 340 | 562 |
| 118 | 205 | 348 | 576 |
| 121 | 210 | 357 | 590 |
| 124 | 215 | 365 | 604 |
| 127 | 221 | 374 | 619 |
| 130 | 226 | 383 | 634 |
| 133 | 232 | 392 | 649 |
| 137 | 237 | 402 | 665 |
| 140 | 243 | 412 | 681 |
| 143 | 249 | 422 | 698 |
| 147 | 255 | 432 | 715 |
| 150 | 261 | 442 | 732 |
| 154 | 267 | 453 | 750 |
| 158 | 274 | 464 | 768 |
| 162 | 280 | 475 | 787 |
| 165 | 287 | — | 806 |
| 169 | — | — | 825 |
Note: The remaining E96 values to complete the 96-step sequence are: 845, 866, 887, 909, 931, 953, 976. (Source: IEC 60063 Standard & Vishay Fixed Resistor Datasheets).
Decade Multipliers vs. Tolerance "Derating"
A common point of confusion for engineers transitioning from NEC wire sizing to component selection is the concept of "derating rows." In wire tables, derating rows reduce ampacity based on ambient heat. The standard resistance table does not derate values; it scales them.
Instead of derating, we use decade multipliers. The base values in the table above represent the significant digits. You multiply them by powers of ten:
- ×100: 47 becomes 47Ω
- ×101: 47 becomes 470Ω
- ×102: 47 becomes 4.7kΩ
- ×103: 47 becomes 47kΩ
However, tolerance acts as a statistical boundary rather than a derating factor. If you specify a 100Ω E24 (5%) resistor, the manufacturer guarantees the physical part will measure between 95Ω and 105Ω at 25°C ambient. The next E24 value up is 110Ω (which spans 104.5Ω to 115.5Ω). Notice the overlap: 105Ω to 104.5Ω. This mathematical overlap ensures that no matter what value you need, a standard component will fall within your acceptable error margin.
What the Standard Resistance Table Cannot Tell You
Knowing the E-series base value is only the first step in component selection. The IEC 60063 table is strictly a nominal value registry. It provides zero information on the physical or environmental limits of the part. When sourcing resistors for a PCB or panel mount, you must independently verify:
- Power Rating (Wattage): A 10kΩ E24 resistor could be a 0.1W 0402 SMD chip or a 5W wirewound ceramic block. The table doesn't specify thermal dissipation limits.
- Temperature Coefficient (Tempco): Measured in ppm/°C. A standard 1% thick-film resistor might drift by ±200 ppm/°C, while a precision thin-film part drifts by ±10 ppm/°C. In high-gain op-amp feedback loops, this drift will destroy your circuit accuracy long before the initial 1% tolerance matters.
- Voltage Coefficient & Maximum Working Voltage: High-value resistors (e.g., 10MΩ) in high-voltage dividers often exhibit non-linear resistance changes under high electric fields. Furthermore, a 1206 SMD resistor typically has a hard maximum working voltage limit of 200V, regardless of its power rating.
- Parasitic Inductance/Capacitance: Wirewound resistors act as inductors at high frequencies. For RF or fast-switching snubber circuits, you must specify non-inductive film or carbon composition types.
Frequently Asked Questions
Why can't I find a 50kΩ or 25kΩ resistor in the E24 series?
Because 50 and 25 are not in the E24 logarithmic sequence. The E24 steps in that decade are 47 and 51 (for the 50s) and 24 and 27 (for the 20s). If your circuit math demands exactly 50.0kΩ, you must either step up to 1% (E96) resistors—which do include 49.9kΩ and 24.9kΩ—or use two standard E24 resistors in series/parallel to synthesize the exact value.
How do I calculate the closest standard value for a custom circuit design?
Use the logarithmic rounding formula. If your target resistance is R, find the nearest base value by calculating the closest match in the E-series table, then apply the appropriate decade multiplier. For example, if you need 34.5kΩ for an ADC divider, look at the E96 table. The closest base values are 340 (34.0kΩ) and 348 (34.8kΩ). 34.8kΩ is the nearest standard 1% value, yielding an error of less than 0.9% from your theoretical target.
Can I substitute an E96 (1%) resistor for an E24 (5%) design?
Yes, almost universally. An E96 resistor is simply a tighter-tolerance version of a resistor. If a schematic calls for a 5% 10kΩ resistor, substituting a 1% 10.0kΩ resistor will only improve the circuit's accuracy. The only exception is if the original design specifically relied on the ±5% drift for a crude thermal compensation effect, which is rare in modern electronics. Note that E24 values are actually a subset of the E96 series (e.g., 10, 11, 12, 13 in E24 map to 100, 110, 121, 130 in E96).
Do standard resistance values apply to capacitors and inductors?
Yes, but typically only the lower series. Capacitors and inductors are generally manufactured to the E6 or E12 series (e.g., 10µF, 22µF, 47µF, 100µF). Because the physical manufacturing tolerances for electrolytic capacitors are often ±20% or worse, and inductors frequently carry ±10% to ±20% tolerances, producing E24 or E96 values for these passive components would be mathematically redundant due to the massive overlap in their tolerance bands.
