The E series is a system of preferred numbers (also called preferred values) derived for use in electronic components. It consists of the E3, E6, E12, E24, E48, E96 and E192 series, where the number after the 'E' designates the quantity of logarithmic value "steps" per decade. Although it is theoretically possible to produce components of any value, in practice the need for inventory simplification has led the industry to settle on the E series for resistors, capacitors, inductors, and zener diodes. Other types of electrical components are either specified by the Renard series (for example fuses) or are defined in relevant product standards (for example IEC 60228 for wires).
During the Golden Age of Radio (1920s to 1950s), numerous companies manufactured vacuum tube based AM radio receivers for consumer use. In the early years, many components were not standardized between numerous AM radio manufacturers. The capacitance values of capacitors (previously called condensers) and resistance values of resistors were not standardized as they are today.
In 1924, the Radio Manufacturers Association (RMA) was formed in Chicago, Illinois by 50 radio manufacturers to license and share patents. Over time, this group created some of the earliest standards for electronics components. In 1936, the RMA adopted a preferred number system for the resistance values of fixed composition resistors. Over time, resistor manufacturers migrated from older values to the 1936 resistance value standard.
During World War II (1940s), American and British military production was a major influence for establishing common standards across many industries, especially in electronics, where it was essential to produce large quantities of standardized electronic parts for military devices, such as wireless communications, radars, radar jammers, LORAN navigation, and more.
Later, the mid-20th century baby boom and the invention of the transistor kicked off demand for consumer electronics goods during the 1950s. As portable transistor radio manufacturing migrated from United States towards Japan during the late-1950s, it was critical for the electronic industry to have international standards.
After being worked on by the RMA, the International Electrotechnical Commission (IEC) began work on an international standard in 1948. The first version of this IEC Publication 63 (IEC 63) was released in 1952. Later, IEC 63 was revised, amended, and renamed into the current version known as IEC 60063:2015.
IEC 60063 release history:
The E series of preferred numbers was chosen such that when a component is manufactured it will end up in a range of roughly equally spaced values (geometric progression) on a logarithmic scale. Each E series subdivides each decade magnitude into steps of 3, 6, 12, 24, 48, 96, 192 values. Subdivisions of E3 to E192 ensure the maximum error will be divided in the order of 40%, 20%, 10%, 5%, 2%, 1%, 0.5%. Also, the E192 series is used for 0.25% and 0.1% tolerance resistors.
Historically, the E series is split into two major groupings:
The formula for each value is determined by the m-th root, but unfortunately the calculated values don't match the official values of all E series.
where:
Vn
m
n
\{0,1,...,m-1\}.
exceptions:
The official values for E48 and E96 series match their calculated values, but all other series (E3 / E6 / E12 / E24 / E192) have one or more official values that don't match their calculated values (see subsets sections below).
For E3 / E6 / E12 / E24, the values from the formula are rounded to 2 significant figures, but eight official values (shown in bold & green) are different from the calculated values (shown in red). During the early half of the 20th century, electronic components had different sets of component values than today. In the late-1940s, standards organizations started working towards codifying a standard set of official component values, and they decided that it wasn't practical to change some of the former established historical values. The first standard was accepted in Paris in 1950, then published as IEC 63 in 1952. The official values of the E3 / E6 / E12 series are subsets of the following official E24 values.
n=\{0,...,23\} | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Calculated Vn | 1.0 | 1.1 | 1.2 | 1.3 | 1.5 | 1.6 | 1.8 | 2.0 | 2.2 | 2.4 | 5.1 | 5.6 | 6.2 | 6.8 | 7.5 | 9.1 | |||||||||
| Official E24 values | 1.0 | 1.1 | 1.2 | 1.3 | 1.5 | 1.6 | 1.8 | 2.0 | 2.2 | 2.4 | 5.1 | 5.6 | 6.2 | 6.8 | 7.5 | 9.1 |
The E3 series is rarely used, except for some components with high variations like electrolytic capacitors, where the given tolerance is often unbalanced between negative and positive such as or, or for components with uncritical values such as pull-up resistors. The calculated constant tangential tolerance for this series gives ( − 1) ÷ ( + 1) = 36.60%, approximately. While the standard only specifies a tolerance greater than 20%, other sources indicate 40% or 50%. Currently, most electrolytic capacitors are manufactured with values in the E6 or E12 series, thus E3 series is mostly obsolete.
For E48 / E96 / E192, the values from the formula are rounded to 3 significant figures, but one value (shown in bold) is different from the calculated values.
m
n
m
n
m
n
n=185
Since some values of the E24 series do not exist in the E48 / E96 / E192 series, some resistor manufacturers have added missing E24 values into of their 1%, 0.5%, 0.25%, 0.1% tolerance resistor families. This allows easier purchasing migration between various tolerances. This E series merging is noted on resistor datasheets and webpages as "E96 + E24" or "E192 + E24". In the following table, the dashed E24 values don't exist in E48 / E96 / E192 series:
| E24 values | 1.0 | 1.1 | 1.2 | 1.3 | 1.5 | 1.6 | 1.8 | 2.0 | 2.2 | 2.4 | 2.7 | 3.0 | 3.3 | 3.6 | 3.9 | 4.3 | 4.7 | 5.1 | 5.6 | 6.2 | 6.8 | 7.5 | 8.2 | 9.1 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| E48 values | 1.00 | 1.10 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | 7.50 | – | – | |
| E96 values | 1.00 | 1.10 | – | 1.30 | 1.50 | – | – | 2.00 | – | – | – | – | – | – | – | – | – | – | – | – | – | 7.50 | – | – | |
| E192 values | 1.00 | 1.10 | 1.20 | 1.30 | 1.50 | 1.60 | 1.80 | 2.00 | – | 2.40 | – | – | – | – | – | – | 4.70 | – | – | – | – | 7.50 | – | – |
If a manufacturer sold resistors with all values in a range of 1 ohm to 10 megaohms, the available resistance values for E3 through E12 would be:
If a manufacturer sold capacitors with all values in a range of 1 pF to 10,000 μF, the available capacitance values for E3 and E6 would be:
List of official values for each E series:
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Printable E series tables