E12

E12 is a designation used in electronics for a standard set of nominal values known as the E-series, defined by the IEC standard IEC 60063. It represents twelve values per decade, spaced so that the ratio between adjacent values is constant and approximately equal to 10^(1/12) (about 1.2115). The base values in a single decade are typically listed as 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. Values for other decades are obtained by multiplying these base numbers by powers of ten (for example, 4.7 Ω, 47 kΩ, 470 kΩ, etc.).

The E12 series is commonly associated with a nominal tolerance of around ±10%, making it suitable for coarse-tolerance components. It is widely used for resistors, and also applies to other fixed-value components where a standard set of values is desirable for ease of manufacturing and stocking.

Compared with finer series such as E24 or E96, the E12 set uses fewer distinct values per decade, which reduces the number of unique parts but can increase layout and design trade-offs in precision applications. The E-series as a whole provides a framework for choosing standardized nominal values and is part of the broader concept of preferred numbers used in electronic component design and production.

See also: E-series, IEC 60063, preferred numbers, resistor values.