E-series of preferred numbers

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This graph shows how almost any value between 1 and 10 is within ±10% of an E12 series value, and its difference from the ideal value in a geometric sequence
Two decades of E12 values, which would give resistor values of 1 Ω to 82 Ω
A decade of the E12 values shown with their electronic color codes on resistors.

The E-series is a system of preferred numbers derived for use in electronics. It consists of the E3, E6, E12, E24, E48, E96 and E192 series.

Overview[edit]

Originally developed in 1948 and 1950, an expanded version was standardized in the international standard IEC 63 (later renamed into IEC 60063) for resistors, capacitors, inductors and Zener diodes by the International Electrotechnical Commission (IEC) in 1963.

It works similarly to the Renard series, except that it subdivides the interval from 1 to 10 into 3, 6, 12 and 24, and later also 48, 96 or 192 steps. These subdivisions ensure that when some arbitrary value is replaced with the nearest preferred number, the maximum relative error will be on the order of 40%, 20%, 10%, 5%, etc.

Use of the IEC or EIA E series is mostly restricted to resistors, capacitors, inductors and Zener diodes. Commonly produced dimensions for other types of electrical components are either chosen from the Renard series instead (for example fuses) or are defined in relevant product standards (for example wires).

The IEC 60063 numbers are as follows. The E6 series is every other element of the E12 series, which is in turn every other element of the E24 series:

E3 (> 20%[nb 1])
E6 (20%)
E12 (10%)
E24 (5%)
1.0 2.2 4.7
1.0 1.5 2.2 3.3 4.7 6.8
1.0 1.2 1.5 1.8 2.2 2.7 3.3 3.9 4.7 5.6 6.8 8.2
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

With the E48 series, a third significant digit is added, and the values are slightly adjusted. Again, the E48 series is every other value of the E96 series, which is every other value of the E192 series:

E48 (2%)
E96 (1%)
E192 (0.5%)
1.00 1.05 1.10 1.15 1.21 1.27 1.33 1.40 1.47 1.54 1.62 1.69 1.78 1.87 1.96 2.05 2.15 2.26 2.37 2.49 2.61 2.74 2.87 3.01 3.16 3.32 3.48 3.65 3.83 4.02 4.22 4.42 4.64 4.87 5.11 5.36 5.62 5.90 6.19 6.49 6.81 7.15 7.50 7.87 8.25 8.66 9.09 9.53
1.00 1.02 1.05 1.07 1.10 1.13 1.15 1.18 1.21 1.24 1.27 1.30 1.33 1.37 1.40 1.43 1.47 1.50 1.54 1.58 1.62 1.65 1.69 1.74 1.78 1.82 1.87 1.91 1.96 2.00 2.05 2.10 2.15 2.21 2.26 2.32 2.37 2.43 2.49 2.55 2.61 2.67 2.74 2.80 2.87 2.94 3.01 3.09 3.16 3.24 3.32 3.40 3.48 3.57 3.65 3.74 3.83 3.92 4.02 4.12 4.22 4.32 4.42 4.53 4.64 4.75 4.87 4.99 5.11 5.23 5.36 5.49 5.62 5.76 5.90 6.04 6.19 6.34 6.49 6.65 6.81 6.98 7.15 7.32 7.50 7.68 7.87 8.06 8.25 8.45 8.66 8.87 9.09 9.31 9.53 9.76
1.00 1.01 1.02 1.04 1.05 1.06 1.07 1.09 1.10 1.11 1.13 1.14 1.15 1.17 1.18 1.20 1.21 1.23 1.24 1.26 1.27 1.29 1.30 1.32 1.33 1.35 1.37 1.38 1.40 1.42 1.43 1.45 1.47 1.49 1.50 1.52 1.54 1.56 1.58 1.60 1.62 1.64 1.65 1.67 1.69 1.72 1.74 1.76 1.78 1.80 1.82 1.84 1.87 1.89 1.91 1.93 1.96 1.98 2.00 2.03 2.05 2.08 2.10 2.13 2.15 2.18 2.21 2.23 2.26 2.29 2.32 2.34 2.37 2.40 2.43 2.46 2.49 2.52 2.55 2.58 2.61 2.64 2.67 2.71 2.74 2.77 2.80 2.84 2.87 2.91 2.94 2.98 3.01 3.05 3.09 3.12 3.16 3.20 3.24 3.28 3.32 3.36 3.40 3.44 3.48 3.52 3.57 3.61 3.65 3.70 3.74 3.79 3.83 3.88 3.92 3.97 4.02 4.07 4.12 4.17 4.22 4.27 4.32 4.37 4.42 4.48 4.53 4.59 4.64 4.70 4.75 4.81 4.87 4.93 4.99 5.05 5.11 5.17 5.23 5.30 5.36 5.42 5.49 5.56 5.62 5.69 5.76 5.83 5.90 5.97 6.04 6.12 6.19 6.26 6.34 6.42 6.49 6.57 6.65 6.73 6.81 6.90 6.98 7.06 7.15 7.23 7.32 7.41 7.50 7.59 7.68 7.77 7.87 7.96 8.06 8.16 8.25 8.35 8.45 8.56 8.66 8.76 8.87 8.98 9.09 9.20 9.31 9.42 9.53 9.65 9.76 9.88

Since the E3 to E24 series were defined and established even before IEC 63, some of the values from 2.7 to 4.7 and 8.2 do not follow the rounding rules exactly, but weren't changed to avoid confusion.

The E192 series is also used for 0.25% and 0.1% tolerance resistors.

1% resistors are available in both the E24 values and the E96 values.

E3 E6 E12 E24 E48 E96 E192
1.00 1.00 1.00 1.00 1.00 1.00 1.00
1.01
1.02 1.02
1.04
1.05 1.05 1.05
1.06
1.07 1.07
1.09
1.10 1.10 1.10 1.10
1.11
1.13 1.13
1.14
1.15 1.15 1.15
1.17
1.18 1.18
1.20
1.20 1.20 1.21 1.21 1.21
1.23
1.24 1.24
1.26
1.27 1.27 1.27
1.29
1.30 1.30
1.32
1.30 1.33 1.33 1.33
1.35
1.37 1.37
1.38
1.40 1.40 1.40
1.42
1.43 1.43
1.45
1.50 1.50 1.50 1.47 1.47 1.47
1.49
1.50 1.50
1.52
1.54 1.54 1.54
1.56
1.58 1.58
1.60
1.60 1.62 1.62 1.62
1.64
1.65 1.65
1.67
1.69 1.69 1.69
1.72
1.74 1.74
1.76
1.80 1.80 1.78 1.78 1.78
1.80
1.82 1.82
1.84
1.87 1.87 1.87
1.89
1.91 1.91
1.93
2.00 1.96 1.96 1.96
1.98
2.00 2.00
2.03
2.05 2.05 2.05
2.08
2.10 2.10
2.13
E3 E6 E12 E24 E48 E96 E192
2.20 2.20 2.20 2.20 2.15 2.15 2.15
2.18
2.21 2.21
2.23
2.26 2.26 2.26
2.29
2.32 2.32
2.34
2.40 2.37 2.37 2.37
2.40
2.43 2.43
2.46
2.49 2.49 2.49
2.52
2.55 2.55
2.58
2.70 2.70 2.61 2.61 2.61
2.64
2.67 2.67
2.71
2.74 2.74 2.74
2.77
2.80 2.80
2.84
3.00 2.87 2.87 2.87
2.91
2.94 2.94
2.98
3.01 3.01 3.01
3.05
3.09 3.09
3.12
3.30 3.30 3.30 3.16 3.16 3.16
3.20
3.24 3.24
3.28
3.32 3.32 3.32
3.36
3.40 3.40
3.44
3.60 3.48 3.48 3.48
3.52
3.57 3.57
3.61
3.65 3.65 3.65
3.70
3.74 3.74
3.79
3.90 3.90 3.83 3.83 3.83
3.88
3.92 3.92
3.97
4.02 4.02 4.02
4.07
4.12 4.12
4.17
4.30 4.22 4.22 4.22
4.27
4.32 4.32
4.37
4.42 4.42 4.42
4.48
4.53 4.53
4.59
E3 E6 E12 E24 E48 E96 E192
4.70 4.70 4.70 4.70 4.64 4.64 4.64
4.70
4.75 4.75
4.81
4.87 4.87 4.87
4.93
4.99 4.99
5.05
5.10 5.11 5.11 5.11
5.17
5.23 5.23
5.30
5.36 5.36 5.36
5.42
5.49 5.49
5.56
5.60 5.60 5.62 5.62 5.62
5.69
5.76 5.76
5.83
5.90 5.90 5.90
5.97
6.04 6.04
6.12
6.20 6.19 6.19 6.19
6.26
6.34 6.34
6.42
6.49 6.49 6.49
6.57
6.65 6.65
6.73
6.80 6.80 6.80 6.81 6.81 6.81
6.90
6.98 6.98
7.06
7.15 7.15 7.15
7.23
7.32 7.32
7.41
7.50 7.50 7.50 7.50
7.59
7.68 7.68
7.77
7.87 7.87 7.87
7.96
8.06 8.06
8.16
8.20 8.20 8.25 8.25 8.25
8.35
8.45 8.45
8.56
8.66 8.66 8.66
8.76
8.87 8.87
8.98
9.10 9.09 9.09 9.09
9.20
9.31 9.31
9.42
9.53 9.53 9.53
9.65
9.76 9.76
9.88

See also[edit]

Notes[edit]

  1. ^ The E3 series is rarely used, except for some components with high variations like electrolytic capacitors, where the given tolerance is often unbalanced such as −30/+50% or −20/+80%, or for components with uncritical values such as pull-up resistors. The calculated tolerance for this series gives (101/3 − 1) ÷ (101/3 + 1) = 36.60%. While the standard only specifies a tolerance greater than 20%, other sources indicate 40% or 50%.

References[edit]

Further reading[edit]

  • IEC 60063: "Preferred number series for resistors and capacitors." (2015)