E12Reihe

The E12-Reihe, also known as the E12 series, is one of the IEC standard series of preferred numbers used for electronic components, especially resistors. It defines twelve values per decade that are spaced logarithmically, allowing a wide range of values to be covered with a compact set of parts. The base values for a decade are: 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, and 8.2. Multiplying these by powers of ten yields all other values within the series, such as 10 Ω, 12 Ω, 15 Ω, 18 Ω, 22 Ω, up to 100 kΩ and beyond.

In practice, E12 values are commonly used with a tolerance of about ±10%. More precise tolerances are provided by other series (such as E24, E48, or E96), which offer additional values per decade for tighter accuracy. The E12 series is widely adopted because it provides a good balance between the number of different resistors needed in stock and the accuracy requirements of many designs.

The E12-Reihe is part of the broader system of preferred numbers defined in the IEC 60063 standard and traces its conceptual roots to Renard series. It is used not only for resistors but also as a general guideline for selecting standard values for capacitors, inductors, and other passive components where standardized, readily available values simplify design and manufacturing.

Examples: 12 kΩ corresponds to 1.2 × 10^4 Ω, and 4.7 kΩ corresponds to 4.7 × 10^3 Ω.