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E24 series

2026-01-16

Takayuki HOSODA

Values such as 22 nF (0.022 μF) or 47 kΩ, which are often found in electronic components, may seem somewhat strange when you encounter them for the first time. Such values are referred to as the E6, E12, and E24 series. They are recommended values for resistors and capacitors, prepared by the International Electrotechnical Commission�fs (IEC) Technical Committee (TC) No.40, "Resistors and Capacitors", and are defined in IEC 60063 (JIS C 5063 in Japan).

Approximate with E24 series E96 series Mixed series ratio product in plane text table CSV

Orign and History

At the 1948 meeting of IEC TC No. 12, Radio-communication, in Stockholm, it was unanimously agreed that one of the most urgent matters for international standardization was a series of recommended values for resistors and capacitors up to 0.1 μF. It might have been desirable to standardize the ¹⁰√10 series system, but in several countries, the ¹²√10 series system had been adopted due to the standardization of 5%, 10%, and 20% tolerance for the aforementioned components. Changing this was unrealistic, so the ¹²√10 system was adopted .
In 1950 a proposal for recommended values for the E6, E12 and E24 series was adopted in Paris, and subsequently published as I.E.C. Publication 63.

The Secret of the E24 Series

Unfortunately, I do not know how the specific numbers were decided by the Technical Committee. However, it turns out that the E24 series subtly deviates from the values rounded to two digits after dividing one digit into 24 equal parts in a geometric progression. This deviation occurs around one third of a digit, between 2.7 and 4.7 (See Table 1).

Table 1 [ E24 / E12 / E6 Series and Geometric Series ]

E24 series (5 % tolerance)	E12 series (10 % tolerance)	E6 series (20 % tolerance)	12√10 Geometric series
1.0	1.0	1.0	1.000
1.1			1.100~
1.2	1.2		1.211~
1.3			1.333~
1.5	1.5	1.5	1.467~
1.6			1.615~
1.8	1.8		1.778~
2.0			1.957~
2.2	2.2	2.2	2.154~
2.4			2.371~
2.7	2.7		2.610~
3.0			2.872~
3.3	3.3	3.3	3.162~
3.6			3.480~
3.9	3.9		3.831~
4.3			4.216~
4.7	4.7	4.7	4.641~
5.1			5.108~
5.6	5.6		5.623~
6.2			6.189~
6.8	6.8	6.8	6.812~
7.5			7.498~
8.2	8.2		8.254~
9.1			9.085~

Thanks to this, you may appreciate the exquisite balance in choosing these values when designing circuits, as you can make the ratio or product of multiple elements a nice value, or slightly larger or smaller. In actual electronic circuits, especially analog circuits, it is often more important to have a product or ratio of values rather than the absolute value of components, such as time constants or the gain of an amplifier. Particularly, thanks to the adoption of '3.0' instead of '2.9', it is truly appreciated that ratios such as

1 : 2 : 4 → 75 : 150 : 300
or
1 : 4 : 5 : 6 : 8 : 9 : 10 : 11 : 12 : 13 : 17 → 3 : 12 : 15 : 18 : 24 : 27 : 30 : 33 : 36 : 39 : 51
or even reciprocally
4 : 6 : 8 : 9 : 12 → 1 / 36 : 1 / 24 : 1 / 18 : 1 / 16 : 1 / 12

Table 2 [Examples of practical magnifications obtained with ratios in the E24 series]

× magnifications	E24 value / E24 value (error)
× 0.268~ ( 2 -√3)	15 / 56 (+0.034%), 22 / 82 (-0.13%)
× 0.293~ ( 1 - 1 / √2)	24 / 82 (+0.072%), 22 / 75 (-0.15%)
× 0.414~ (√2 - 1)	91 / 22 (+0.14%), 6.2 / 15 (+0.21%)
× 0.732~ (√3 - 1)	11 / 15 (-0.18%), 22 / 30 (-0.18%)
× 1.1	11 / 10, 22 / 20, 33 / 30
× 1.2 (6 / 5)	12 / 10, 18 / 15, 24 / 20, 36 / 30
× 1.25 (5 / 4)	15 / 12, 20 / 16, 30 / 24
× 1.33~ (4 / 3)	100 / 75, 16 / 12, 20 / 15, 24 / 18, 36 / 27, 68 / 51
× 1.4 (7 / 5)	18 / 13 (-1.1%)
× 1.41 (√2)	51 / 36 (-0.17%), 130 / 91 (-1.0%)
× 1.5 (3 / 2)	15 / 10, 18 / 12, 24 / 16, 27 / 18, 30 / 20, 33 / 22, 36 / 24
× 1.6 (8 / 5)	120 / 75, 16 / 10
× 1.66~ (5 / 3)	20 / 12, 30 / 18
× 1.73 (√3)	130 / 75 (-0.07%)
× 1.75 (7 / 4)	82 / 47 (-0.3%)
× 1.8 (9 / 5)	18 / 10, 27 / 15, 36 / 20
× 2	150 / 75, 20 / 10, 22 / 11, 24 / 12, 30 / 15, 36 / 18
× 2.16~ (√10 - 1)	39 / 18 (+0.2%), 11 / 51 (+0.25%)
× 2.2 (11 / 5)	22 / 10, 33 / 15
× 2.25 (9 / 4)	27 / 12, 36 / 16
× 2.33~ (7 / 3)	56 / 24, 91 / 39
× 2.5 (5 / 2)	30 / 12, 75 / 30
× 2.6 (13 / 5)	39 / 15
× 2.66~ (8 / 3)	200 / 75
× 2.75 (11 / 4)	33 / 12
× 2.8 (14 / 5)	56 / 20
× 3	3 / 1, 33 / 11, 36 / 12, 39 / 13
× 3.16~ (√10)	16 / 5.1 (+0.78%), 51 / 16 (+0.79%)
× 3.2 (16 / 5)	240 / 75
× 3.25 (13 / 4)	39 / 12
× 3.4 (17 / 5)	51 / 15, 68 / 20
× 3.5 (7 / 2)	56 / 16
× 3.75 (15 / 4)	75 / 20
× 4	12 / 3, 300 / 75
× 4.25 (17 / 4)	51 / 12, 68 / 16
× 4.5 (9 / 2)	68 / 15 (+0.7%)
× 5	75 / 15, 10 / 20, 11 / 22, 12 / 24, 15 / 3, 180 / 36
× 5.5 (11 / 2)	11 / 2
× 6	12 / 2, 18 / 3
× 6.5 (13 / 2)	13 / 2
× 7	91 / 13
× 7.5 (15 / 2)	120 / 16, 15 / 2, 180 / 24, 270 / 36, 510 / 68, 75 / 10
× 8	120 / 15, 16 / 2, 24 / 3
× 8.5 (16 / 2)	330 / 39 (+0.45%)
× 9	18 / 2, 27 / 3

The E24 series was likely designed with consideration for both a just intonation scale (akin to a pure tone scale) and a well-tempered scale (akin to a mean scale), in order to facilitate the realization of favorable ratios.

Appendix A — Tolerances code of resistors

Resistance tolerances are mainly determined by rounding the R3 series (Renard numbers) to the nearest digit, primarily using the 1-2-5 series.

Table 3 [Example of tolerance code]

code	tolerance [%]	series	color code
(S)	0.0010
(U)	0.0020
(X)	0.0025
E(V)	0.0050
L(T)	0.01		(Grey)
P(H)	0.02		(Yellow)
W(A)	0.05		Orange
B	0.10		Purple
C	0.25		Blue
D	0.50	E192	Green
F	1	E96	Brown
G	2	E48	Red
J	5	E24	Gold
K	10	E12	Silver
M	20	E6	plane

Compliant with IEC60062:2016 (JIS C 5062, JIS C 60062:2019 in Japan).
The code in parentheses () are examples of extensions by resistor manufacturers (e.g. Vishay).

Appendix B — Rated voltage of capacitors and their codes

The capacitance of capacitors primarily uses the E series, such as E6 or E12. However, the rated voltage uses values based on the R10 standard numbers (Renard numbers). The rated voltage of the capacitor represents the exponent as a number in the first character and the mantissa as an uppercase English letter in the second character. The mantissa corresponds to the R10 standard numbers {1.0, 1.25, 1.6, 2.0, 2.5, 3.15, 4.0, 5.0, 6.3, 8.0} with {A, B, C, D, E, F, G, H, J, K}.

Table 4 [Examples of rated voltages and their codes]

Code	Tolerance [V]
0E	2.5
0G	4.0
0L	5.5
0J	6.3
1A	10
1B	12.5
1C	16
1D	20
1E	25
(1V)	35
1G	40
1H	50
1J	63
1K	80
2A	100
(2Q)	110
2B	125
2C	160
(2P)	180
2D	200
2E	250
2F	315
(2V)	350
2G	400
(2W)	450
2H	500
2J	630
3A	1000
3B	1250
3C	1600
3D	2000

Compliant with IEC 60384-1:2016 (JIS C 5101-1:2019 in Japan)
The code in parentheses () are examples of extensions by resistor manufacturers.

As an aside, in JIS C 5101-1:2010 (IEC 60384-1:2008) under

2.3.3 Recommended values of rated voltage

there was a note stating

Note 2: In particular, if necessary, the rated voltages of 35V, 350V, and 450V from the R20 standard number series may be used.

However, this statement was removed in JIS C 5101-1:2019 2.3.3.

Column — 350V or 450V

Modern power-supply designs are increasingly converging on a DC bus voltage around 400 V, driven by the widespread adoption of universal input and active PFC stages. As a result, rated voltages such as 275 V, 315 V, and 350 V, which were once well aligned with rectified mains systems, are gradually losing their architectural relevance. In contrast, 450 V and 500 V provide a more practical margin above the 400 V DC bus and are widely used in applications such as EVs, UPS systems, and industrial inverters, where high production volumes support long-term availability. For film and electrolytic capacitors, the rated voltage is not merely a matter of margin: it directly affects dielectric thickness, package size, and cost, making it difficult to substitute parts once certain voltage classes disappear from the market. For this reason, in new designs it is advisable not only to consider the immediate electrical requirements, but also to take into account the likely long-term availability of voltage classes such as 450 V, 500 V, and 630 V.

Appendix C — Codes for temperature characteristics of Class-1 ceramic capacitors

Table 5 [Temperature Coefficients TC of Class-1 ceramic capacitors]

Code	TC ppm / °C	TC tolerance ppm	Color code
C0G	0	±30	Black
P2G	-150	±30	Orange
R2G	-220	±30	Yellow
S2H	-330	±60	Green
T2H	-470	±60	Blue
U2J	-750	±120	Violet
SL	+350 ∼ -1000		Gray

Excerpt from IEC 60384-8:2015 (JIS C 5101-8:2018 in Japan)

Ceramic capacitors for temperature compensation other than zero temperature coefficient (C0G, NP0 characteristics, etc.) are almost extinct as of 2023, leaving only a few with P2G and U2J characteristics.

Appendix D - Table D �\ EIA-96 3-digit marking code for SMD resistors

code#	value	code#	value	code#	value	code#	value
01#	100	02#	102	03#	105	04#	107
05#	110	06#	113	07#	115	08#	118
09#	121	10#	124	11#	127	12#	130
13#	133	14#	137	15#	140	16#	143
17#	147	18#	150	19#	154	20#	158
21#	162	22#	165	23#	169	24#	174
25#	178	26#	182	27#	187	28#	191
29#	196	30#	200	31#	205	32#	210
33#	215	34#	221	35#	226	36#	232
37#	237	38#	243	39#	249	40#	255
41#	261	42#	267	43#	274	44#	280
45#	287	46#	294	47#	301	48#	309
49#	316	50#	324	51#	332	52#	340
53#	348	54#	357	55#	365	56#	374
57#	383	58#	392	59#	402	60#	412
61#	422	62#	432	63#	442	64#	453
65#	464	66#	475	67#	487	68#	499
69#	511	70#	523	71#	536	72#	549
73#	562	74#	576	75#	590	76#	604
77#	619	78#	634	79#	649	80#	665
81#	681	82#	698	83#	715	84#	732
85#	750	86#	768	87#	787	88#	806
89#	825	90#	845	91#	866	92#	887
93#	909	94#	931	95#	953	96#	976

# EIA-96 SMD resistor multiplication factors:
Z       0.001
Y | R   0.01
X | S   0.1
A       1
B | H   10
C       100
D       1000
E       10000
F       100000
e.g. 84C : 732 x 100 = 73.2 kOhm

Note:
R is the traditional radix-point symbol in resistor markings (cf. IEC 60062 RKM code).
S and H originate from legacy Asian manufacturer marking systems, but are not defined in the EIA-96 specification.

Revision History

▼ unfold / fold

[Jan. 15, 2026] Rev.1.60
[July 31, 2024] Rev.1.50
[July 17, 2024] Rev.1.47
[July 13, 2024] Rev.1.46
[May  15, 2023] Rev.1.45
[May   2, 2023] Rev.1.44
[June 27, 2019] Rev.1.43
[Apr. 18, 2018] Rev.1.42
[Feb. 12, 2015] Rev.1.41
[July  5, 2014] Rev.1.4 
[Nov. 18, 2014] Rev.1.31
[Apr. 13, 2012] Rev.1.3 
[May   7, 2009] Rev.1.2
[Apr. 23, 2009] Rev.1.1
[Apr. 22, 2009] Rev.1.0

This article is a modified version of the E24 series article that appeared in the May 2008 issue of Transistor Technology.

REFERENCE

1. CSI IEC 60063, PREFERRED NUMBER SERIES FORRESISTORS AND CAPACITORS
2. Takayuki HOSODA, "Q1-2 Why are the resistor values 1, 2.2, 3.3, 4.7 ... so close together?", Transistor Technology, May 2008, p.p.104-105, CQ Publishing

SEE ALSO

• Find the nearest fraction in the E24 numbers (for HP 42S)
• Find the nearest fraction in the E24 numbers (for HP 35s)

External links

• Preferred number - E24 numbers defined in the IEC 60063 (JIS C 5063)