E12serien

E12serien, commonly known as the E12 series, is a standardized set of preferred numerical values used to label electronic component values, especially fixed resistors and capacitors. It is part of a family of IEC standard series defined by the International Electrotechnical Commission in IEC 60063. The E12 series comprises twelve values per decade, chosen to be roughly equally spaced on a logarithmic scale. The nominal values in the E12 series 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. By multiplying by powers of ten, these values cover a wide range of component sizes.

Adjacent values differ by a factor of approximately 1.2115, corresponding to 10^(1/12). The series is designed to provide a practical balance between standardization and the ability to approximate a desired value with a reasonable tolerance. In practice, E12 values are most commonly used with tolerances around ±10% for fixed resistors and capacitors, though the actual tolerance depends on the component type and specification. For applications requiring finer granularity, other series in the IEC family (for example E24, E48, E96) are used.

The E12 series remains widely used in electronics design and manufacturing, particularly for consumer electronics where cost and ease of sourcing are important. It interacts with component standards and procurement catalogs and is part of broader standardization efforts for numerical labels and values.

See also: IEC 60063, preferred numbers; E24, E96 series.