IEC 62358:2026

IEC 62358 ®
Edition 3.0 2026-01
INTERNATIONAL
STANDARD
REDLINE VERSION
Ferrite cores - Standard inductance factor for gapped cores and its tolerance
ICS 29.100.10 ISBN 978-2-8327-1000-5
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CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Measuring method . 6
5 A value and its tolerance . 7
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5.1 General . 7
5.2 Tolerance . 7
5.3 E-core . 7
5.4 ETD-core and EER-core . 7
5.5 EP-core . 7
5.6 RM-core . 7
5.7 Pot-core . 7
5.8 PQ-core . 7
5.9 Low-profile core . 7
5.10 PM-cores . 8
5.11 EC-cores . 8
5.12 EFD-cores . 8
Bibliography . 21

Table 1 – Tolerance versus letter code . 7
Table 2 – A and its tolerance for E-cores (IEC 62317-8 IEC 63093-8) . 9
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Table 3 – A and its tolerance for ETD-cores (IEC 61185 IEC 63093-6) and EER-cores
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(IEC 62317-7 IEC 63093-7) . 10
Table 4 – A and its tolerance for EP-cores (IEC 61596 IEC 63093-5) . 11
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Table 5 – A and its tolerance for RM-cores (IEC 62317-4 IEC 63093-4) . 12
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Table 6 – A and its tolerance for Pot-cores (IEC 62317-2 IEC 63093-2) . 12
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Table 7 – A and its tolerance for PQ-cores (IEC 62317-13 IEC 63093-13) . 13
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Table 8 – A and its tolerance for EL-cores (IEC 62317-9 IEC 63093-9) . 14
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Table 9 – A and its tolerance for EL-I (plate)-cores (IEC 62317-9 IEC 63093-9) . 14
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Table 10 – A and its tolerance for low-profile ER-I (plate)-cores (IEC 62317-9
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IEC 63093-9) . 15
Table 11 – A and its tolerance for low-profile ER-cores (IEC 62317-9 IEC 63093-9) . 16
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Table 12 – A and its tolerance for low-profile E-I (plate)-cores (IEC 62317-9
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IEC 63093-9) . 17
Table 13 – A and its tolerance for low-profile E-cores (IEC 62317-9 IEC 63093-9) . 17
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Table 14 – A and its tolerance for low-profile RM cores (IEC 62317-4 IEC 63093-4) . 18
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Table 15 – A and its tolerance for low-profile PQ-I (plate)-cores (IEC 62317-13
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IEC 63093-13) . 18
Table 16 – A and its tolerance for PM-cores (IEC 63093-10) . 19
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Table 17 – A and its tolerance for EC-cores (IEC 63093-11) . 19
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Table 18 – A and its tolerance for EFD-cores (IEC 63093-14) . 20
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Ferrite cores -
Standard inductance factor for gapped cores and its tolerance

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
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shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes made
to the previous edition IEC 62358:2012. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

IEC 62358 has been prepared by IEC technical committee 51: Magnetic components, ferrite
and magnetic powder materials. It is an International Standard.
This third edition cancels and replaces the second edition published in 2012. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) addition of A value (inductance factor) and its tolerance for PM-cores;
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b) addition of A value (inductance factor) and its tolerance for EC-cores;
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c) addition of A value (inductance factor) and its tolerance for EFD-cores.
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The text of this International Standard is based on the following documents:
Draft Report on voting
51/1583/FDIS 51/1595/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
– reconfirmed,
– withdrawn, or
– revised.
INTRODUCTION
The A value (inductance factor) and its tolerance have been specified by the users before.
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When manufacturers wish to have an inventory for short delivery, they have to hold the products
before gapping since there is no standard for the A value. Because of electronic commerce
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and the increased demand for rapid delivery of products, it will be more convenient for
customers and suppliers to refer to established A values and tolerances. This standard has
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been developed to meet this demand.
As a result of the implementation of this standard, it will be easier for core suppliers and users
to develop electronic components using gapped soft ferrite cores. Conventional businesses will
benefit, as will new companies working in new fields such as e-commerce.
It is recommended that users specify A values by selecting them from this standard. The
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tolerances in this standard are recommended, but for historical reasons a manufacturer’s
specification might differ for some components. Users should confirm tolerances from the
manufacturer's literature. Manufacturers are encouraged to use the A values in this standard
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when building stocks of gapped cores for short delivery. In cases where users or manufacturers
specify a gap length with tolerances the A value will only be approximate and without tolerance.
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Such cases will be outside the scope of this standard.
The A value (inductance factor) and its tolerance is a critical design parameter for gapped
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ferrite core sets. For any core size, there is a wide range of possible gapped A values, and
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there is no technical reason why a user could not select any precise value within the possible
range. But as a practical matter, there are advantages to the users that certain values within
the range are identified to be standard and to the users in selecting those values where possible.
The potential advantages include faster delivery from supplier inventories of standard gapped
parts, greater ease of obtaining small quantities for development sampling and low-volume
projects, interchangeability among multiple applications, reduced risk of dead inventories,
economies of scale from producing larger batches, and standardized tolerancing across
multiple suppliers.
It is important that users specify A values by selecting them from this document when possible.
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The tolerances shown in this document are selected for suitable performance with best cost
and full interchangeability. Suppliers may offer tighter tolerances for their standard parts while
remaining in compliance with the standard. Users can require tighter tolerances for specific
applications.
In cases where users or suppliers specify a physical gap length with tolerances, then the A
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value will only be approximate and without tolerance. It is generally true that better
measurement precision and better consistency in application performance is achieved by
specifying the A value and not the gap dimension. The exceptions are cases in which the gap
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is quite large, where users can find that their application coil gives a more consistent result if
the gap dimension is controlled directly and the A value as measured in the supplier's standard
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coil is allowed to vary.
1 Scope
This document provides standard A values (inductance factors) and their tolerances of Pot,
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RM, ETD, E, EER, EP, PQ, PM, EC, EFD and low-profile gapped ferrite cores.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 61185, Ferrite cores (ETD-cores) intended for use in power supply applications –
Dimensions
IEC 61596, Magnetic oxide EP-cores and associated parts for use in inductors and transformers
– Dimensions
IEC 62044-2, Cores made of soft magnetic materials - Measuring methods - Part 2: Magnetic
properties at low excitation level
IEC 62317-2, Ferrite cores – Dimensions – Part 2: Pot-cores for use in telecommunications,
power supply, and filter applications
IEC 62317-4, Ferrite cores – Dimensions – Part 4: RM-cores and associated parts
IEC 62317-7, Ferrite cores – Dimensions – Part 7: EER-cores
IEC 62317-8, Ferrite cores – Dimensions – Part 8: E-cores
IEC 62317-9, Ferrite cores – Dimensions – Part 9: Planar cores
IEC 62317-13, Ferrite cores – Dimensions – Part 13: PQ-cores for use in power supply
applications
ISO 497, Guide to the choice of series of preferred numbers and of series containing more
rounded values of preferred numbers
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
4 Measuring method
The method for measuring the inductance factor shall be in accordance with IEC 62044-2.
5 A value and its tolerance
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5.1 General
The series of preferred numbers of the A value shall be selected from the R10 series of ISO 497.
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5.2 Tolerance
The tolerance shall be selected from Table 1, which specifies letter codes for the tolerances.
Table 1 – Tolerance versus letter code
Tolerance % ±3 ±5 ±7 ±10 ±12 ±15 ±20
Letter code A J E K H L M
5.3 E-core
The A value and its tolerance for E-cores shall be selected from Table 2.
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NOTE The E-core is a pair of an E-shape core.
5.4 ETD-core and EER-core
The A value and its tolerance for ETD-cores and EER-cores shall be selected from Table 3.
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5.5 EP-core
The A value and its tolerance for EP-cores shall be selected from Table 4.
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5.6 RM-core
The A value and its tolerance for RM-cores shall be selected from Table 5.
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5.7 Pot-core
The A value and its tolerance for Pot-cores shall be selected from Table 6.
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5.8 PQ-core
The A value and its tolerance for PQ-cores shall be selected from Table 7.
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5.9 Low-profile core
– The A value and its tolerance for EL-cores shall be selected from Table 8 and Table 9.
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– The A value and its tolerance for low-profile ER-cores shall be selected from Table 10 and
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Table 11.
– The A value and its tolerance for low-profile E-cores shall be selected from Table 12 and
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Table 13.
– The A value and its tolerance for low-profile RM-cores shall be selected from Table 14.
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– The A value and its tolerance for low-profile PQ-I (plate)-cores shall be selected from
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Table 15.
5.10 PM-cores
The A value and its tolerance for PM-cores shall be selected from Table 16.
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5.11 EC-cores
The A value and its tolerance for EC-cores shall be selected from Table 17.
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5.12 EFD-cores
value and its tolerance for EFD-cores shall be selected from Table 18.
The A
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Table 2 – A and its tolerance for E-cores (IEC 62317-8 IEC 63093-8)
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A (nH/N ) tolerance in ± %
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IEC references
Industrial references
core size
A12,5 A16 A20 A25 A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800
E5,3/2 FEE5,25 EE5 10 10 15 20
E6,3/2 FEE6,18 10 10 15 20
E8/2 FEE8 5 7 10 10 15 20
E8,3/4 FEE8,3; EE8  7 7 10 12 15 20
E8,8/2 FEE9 7 7 10 15 20
E10/3 FEE10  5 5 7 10 12 15
E10,2/5 FEE10,2; EE10 x /11  5 5 7 10 10 15
E13/4 FEE12,7A; EF12,6  5 5 7 7 10 12 15
E13/6 EE13   5 5 7 10 12 15
E16/4,8 FEE16A; EE16   5 5 7 10 10 12
E16/5 FEE16,1; EF16   5 5 7 10 10 12 15
E19/5 FEE19A; EE19   3 5 7 10 10 10 15
E19,3/4,8 EE-187; EE19 x /16   3 5 7 10 10 10 15
E20/6 FEE20,1; EF20    3 5 7 7 10 10 12
E25/7 FEE25,1; EF25    3 3 5 7 7 10 10 12
E25,4/6 FEE25,4A    3 5 7 7 10 10 12
E25,4/6,3 EE24 x /25; EE25 x /19    3 5 7 7 10 10 12
E30/11 FEE30A; EE30     3 3 3 3 5 7 7 10 10 10
E32/9 FEE32,1; EF32     3 3 3 5 7 7 7 10 12
E33/13 FEE33A; EE33     3 3 3 5 5 7 10 10 10
E34,6/9 EE375; EE35/28B      3 5 7 7 10 10 10
E35/10 FEE35A; EE35      3 5 5 7 7 10 10 15
E40/11 FEE40A; EE40      3 3 5 7 7 10 10 10
E41/13 EE21; EE41/33C      3 3 3 5 5 7 10 10

A (nH/N ) tolerance in ± %
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IEC references
Industrial references
core size
A12,5 A16 A20 A25 A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800
E42/15 FEE42A      3 3 3 3 5 7 7 10
E42/20 FEE42B      3 3 3 3 3 7 7 10
E47/16 EE625; EE47 x /39      5 5 5 5 7 7 10 12
E50/15 EE50A; EE50      5 5 5 5 7 10 10 15
E55/21 FEE55,2A      3 5 5 5 5 5 7 10
E55/25 FEE55,2B      5 5 5 5 5 5 7 7
E60/16 FEE60A; EE60      3 5 5 7 7 10 12
E65/27 FEE65,2       3 5 5 5 5 5 7
NOTE To guarantee the tolerances in this table, 0,25 AQL (acceptable quality level) is applied.

Table 3 – A and its tolerance for ETD-cores (IEC 61185 IEC 63093-6) and EER-cores (IEC 62317-7 IEC 63093-7)
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IEC references
A (nH/N ) tolerance in ± %
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core size
A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630
ETD19 3 3 5 7 7 10
ETD24 3 3 5 7 7 10 10
ETD29  3 3 5 7 7 10 10 12
ETD34  3 3 5 7 7 10 10 12
ETD39   3 3 5 5 7 10 10
ETD44   3 5 5 7 10 10 15
ETD49   3 5 5 7 10 12 15
ETD54   5 5 5 5 7 10 10
ETD59   5 5 5 5 5 7 10
EER25,5 3 3 7 7 10 10 10
EER28  3 3 5 5 7 10 10 10
IEC references
A (nH/N ) tolerance in ± %
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core size
A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630
EER28L  3 3 5 5 7 10 10 10
EER35  3 3 5 5 7 10 10 10
EER39   3 3 5 5 7 10 10
EER40   3 3 3 5 7 7 10
EER42   3 5 5 7 10 10 15
EER49   3 5 5 7 10 10 12
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 4 – A and its tolerance for EP-cores (IEC 61596 IEC 63093-5)
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A (nH/N ) tolerance in ± %
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IEC references
core size
A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800 A1 000
EP5 12 15
EP7 3 3 3 3 5 5 7 10 10
EP10 3 3 3 3 5 5 7 10 10
EP13 3 3 3 3 3 5 5 7 7 10
EP17  3 3 3 3 3 3 5 5 7 7 10
EP20   3 3 3 3 3 3 5 5 7 7
EP30       5 5
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 5 – A and its tolerance for RM-cores (IEC 62317-4 IEC 63093-4)
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A (nH/N ) tolerance in ± %
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IEC references
core size
A25 A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800 A1 000 A1 250 A1 600 A2 000
RM4 3 3 3 5 5 5 7 7 10
RM5  3 3 3 3 3 5 5 5 7
RM6S  3 3 3 3 3 3 5 5 5
RM6R  3 3 3 3 3 3 3 5 5
RM7   3 3 3 3 3 5 5 5 7 10
RM8    3 3 3 3 3 3 5 5 7 10
RM10    3 3 3 3 3 3 3 3 5 5 7 10
RM12    3 3 3 3 3 3 3 5 5 7 10 10
RM14     3 3 3 3 3 5 5 7 10 10 12
RM14A     3 3 3 3 3 3 5 5 7 7 10 12
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 6 – A and its tolerance for Pot-cores (IEC 62317-2 IEC 63093-2)
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IEC references
A (nH/N ) tolerance in ± %
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core size
A25 A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800 A1 000 A1 250 A1 600 A2 000
mm
P5,8 × /3,3 3 5 5 7 10 12
3 3 5 5 7 7 10
P7,4 × /4,0
3 3 3 5 5 7 10
P9 × /5
P11 × /7   3 3 3 5 5 7 10
3 3 5 5 5 7 10
P14 × /8
3 3 3 3 3 5 5 7 10
P18 × /11
P22 ×/13    3 3 3 3 3 3 3 5 5 7 10

IEC references
A (nH/N ) tolerance in ± %
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core size
A25 A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800 A1 000 A1 250 A1 600 A2 000
mm
3 3 3 3 3 3 3 3 5 5 7
P26 × /16
P30 × /19     3 3 3 3 3 3 3 3 5 5
P36 × /22      3 3 3 3 3 3 3 5 5
3 3 3 3 3 3 3 3 5 5
P42 × /29
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 7 – A and its tolerance for PQ-cores (IEC 62317-13 IEC 63093-13)
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IEC references
A (nH/N ) tolerance in ± %
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core size
A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800 A1 000
mm
PQ16/11,6 3 5 5 7 10 12 15
PQ20/16 3 3 5 5 5 7 10 10 12
PQ20/20 3 3 5 5 5 7 10 10 12
PQ26/20 3 3 3 3 5 5 5 7 10
PQ26/25 3 3 3 3 5 5 5 7 10
PQ32/20 3 3 3 3 3 5 5 7 7 10
PQ32/30 3 3 3 3 3 5 5 7 7 10
PQ35/35 3 3 3 3 3 3 5 5 7 7 10
PQ40/40 3 3 3 3 3 3 5 5 7 7 10
PQ50/50 3 3 3 3 3 5 5 7 7 10 12
PQ65/54     5 5 7 10
PQ78/39    5 5 7 10 10
PQ107/87     5 5 7
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 8 – A and its tolerance for EL-cores (IEC 62317-9 IEC 63093-9)
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IEC references
A (nH/N ) tolerance in ± %
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Core size
A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400
mm
3 3 3 5 5 7 7 10
EL-EL11 × 4,0
EL-EL13 × 4,4 3 3 3 3 3 5 5 7 10
EL-EL15,5 × 5,8 3 3 3 3 3 5 5 7 7
3 3 3 3 3 3 5 5 5 7
EL-EL18 × 7,3
3 3 3 3 3 3 3 5 5 5
EL-EL20 × 7,7
EL-EL22 × 8,0  3 3 3 3 3 3 5 5 7
3 3 3 3 3 3 3 5 5
EL-EL25 × 8,6
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 9 – A and its tolerance for EL-I (plate)-cores (IEC 62317-9 IEC 63093-9)
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IEC references
A (nH/N ) tolerance in ± %
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core size
A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400
mm
EL-PLT11 × 4,0 3 3 3 5 5 7 7 10
3 3 3 3 3 5 5 7 10
EL-PLT13 × 4,4
EL-PLT15,5 × 5,8 3 3 3 3 3 5 5 7 7
EL-PLT18 × 7,3 3 3 3 3 3 3 5 5 5 7
3 3 3 3 3 3 3 5 5 5
EL-PLT20 × 7,7
EL-PLT22 × 8,0  3 3 3 3 3 3 5 5 7
EL-PLT25 × 8,6  3 3 3 3 3 3 3 5 5
3 3 3 3 3 5 5 7 10
EL-PLT11 × 3,0
3 3 3 3 3 5 5 7 10
EL-PLT13 × 3,4
EL-PLT15,5 × 4,3 3 3 3 3 3 5 5 7 7

IEC references
A (nH/N ) tolerance in ± %
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core size
A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400
mm
3 3 3 3 3 3 5 5 5 7
EL-PLT18 × 5,3
EL-PLT20 × 5,7 3 3 3 3 3 3 3 5 5 5
EL-PLT22 × 6,0  3 3 3 3 3 3 5 5 7
3 3 3 3 3 3 3 5 5
EL-PLT25 × 6,6
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 10 – A and its tolerance for low-profile ER-I (plate)-cores (IEC 62317-9 IEC 63093-9)
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IEC references
A (nH/N ) tolerance in ± %
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core size
A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800 A1 000 A1 250
mm
3 5 5 7 7 10 12
ER9,5 ×2,5 × 5 / PLT9,5 × 1 × 5
ER11 × 2,5 × 6 / PLT11 × 1 × 6 3 3 3 5 5 7 10 12 15
ER13 × 3 × 9 / PLT13 × 1 × 9 3 3 3 3 5 5 7 7 10
ER14,5 × 3 × 7 / PLT14,5 × 1 × 7 3 3 3 3 5 5 7 7 10
ER18 × 3 × 10 / PLT18 × 1,5 × 10  3 3 3 3 5 5 7 10 10
ER20 × 6 × 14 / PLT20 × 2 × 14   3 3 3 3 3 5 5 7 10
ER23 × 3,6 × 13 / PLT23 × 2 × 13   3 3 3 3 5 5 7 7 10
3 3 3 3 5 5 7 7 10
ER23 × 5 × 13 / PLT23 × 2 × 13
ER25 × 6 × 15 / PLT25 ×2,4 ×15   3 3 3 3 3 5 7 7 10
ER25 × 6 × 18 / PLT25 × 2 × 18   3 3 3 3 5 5 7 7 10
3 3 3 3 5 5 7 7 10
ER30 × 8 × 20 / PLT30 × 3 × 20
ER32 × 5 × 21 / PLT32 × 2 × 21   3 3 3 3 5 5 7 7 10
ER32 × 6 × 25 / PLT32 × 3 × 25    3 3 3 3 5 5 7 7 10
ER35 × 10 × 26 / PLT35× 5 × 26    3 3 3 3 3 5 5 7 10
ER40 × 10 × 28 / PLT40 × 5 × 28    3 3 3 3 3 5 5 7 10
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 11 – A and its tolerance for low-profile ER-cores (IEC 62317-9 IEC 63093-9)
L
IEC references
A (nH/N ) tolerance in ± %
L
core size
A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800 A1 000 A1 250
mm
ER9,5 × 2,5 x 5 3 5 5 7 7 10 12
ER11 × 2,5 x 6 3 3 3 5 5 7 10 12 15
ER13 × 3 × 9 3 3 3 3 5 5 7 7 10

ER14,5 × 3 x 7 3 3 3 3 5 5 7 7 10

ER18 × 3 × 10 3 3 3 3 5 5 7 10 10
ER20 × 6 × 14   3 3 3 3 3 5 5 7 10
3 3 3 3 5 5 7 7 10
ER23 × 3,6 × 13
ER23 × 5 × 13 3 3 3 3 5 5 7 7 10
ER25 × 6 × 15   3 3 3 3 3 5 7 7 10
ER25 × 6 × 18   3 3 3 3 5 5 7 7 10

ER25 × 8 × 18 3 3 3 3 5 5 7 7 10
3 3 3 3 5 5 7 7 10
ER30 × 8 × 20
ER32 × 5 × 21   3 3 3 3 5 5 7 7 10
ER32 × 6 × 25    3 3 3 3 5 5 7 7 10
3 3 3 3 3 5 5 7 10
ER35 × 10 × 2726
ER40 × 10 × 3228 3 3 3 3 3 5 5 7 10
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 12 – A and its tolerance for low-profile E-I (plate)-cores (IEC 62317-9 IEC 63093-9)
L
A (nH/N ) tolerance in ± %
L
IEC references
core size
A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800 A1 000
E-PLT14 3 5 5 7 10 12 15
E-PLT18 3 3 3 3 5 5 7 10
E-PLT22  3 3 3 3 3 3 5 5 7
E-PLT32   3 3 3 3 5 5 7
E-PLT38   3 3 3 3 3 3 5 5 7
E-PLT43   3 3 3 3 3 3 5 7
E-PLT58    3 3 3 3 3 5 7 7
E-PLT64    3 3 3 3 3 3 5 5
E-PLT102     3 3 3 3 3 5 5
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 13 – A and its tolerance for low-profile E-cores (IEC 62317-9 IEC 63093-9)
L
A (nH/N ) tolerance in ± %
IEC references L
core size
A50 A63 A80 A100 A160 A250 A315 A400 A500 A630 A800 A1 000
A40 A125 A200
3 5 5 7 10 12
E-E14
3 3 3 3 5 5 7 10
E-E18
3 3 3 3 3 3 5 5 7
E-E22
3 3 3 3 5 5 7
E-E32
3 3 3 3 3 3 5 5 7
E-E38
3 3 3 3 3 3 5 5
E-E43
3 3 3 3 3 5 7 10
E-E58
3 3 3 3 3 3 5 5
E-E64
3 3 3 3 3 5 5
E-E102
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.,

Table 14 – A and its tolerance for low-profile RM cores (IEC 62317-4 IEC 63093-4)
L
IEC references
A (nH/N ) tolerance in ± %
L
core size
A25 A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315 A400 A500 A630 A800 A1 000 A1 250 A1 600 A2 000
mm
RM4/8 3 3 3 3 5 5 7 7 10
RM5/8 3 3 3 3 3 3 5 5 7 10
RM6/9  3 3 3 3 3 3 3 5 5
RM7/10  3 3 3 3 3 3 3 5 5 7 7
RM8/11   3 3 3 3 3 3 3 5 5 7 7 10
RM10/13   3 3 3 3 3 3 3 3 5 5 7 7 10
RM12/17    3 3 3 3 3 3 3 3 3 5 5 7 7
RM14/20     3 3 3 3 3 3 3 3 3 5 5 7
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 15 – A and its tolerance for low-profile PQ-I (plate)-cores (IEC 62317-13 IEC 63093-13)
L
IEC references
A (nH/N ) tolerance in ± %
L
core size
A63 A80 A100 A125 A160 A200 A250 A315 A400 A500
mm
PQ-I (plate) 16/7,8 3 5 5 7 7 10 10 12
PQ-I (plate) 20/9 3 3 3 5 7 7 7 10
PQ-I (plate) 26/12  3 3 3 3 5 5 5 7
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 16 – A and its tolerance for PM-cores (IEC 63093-10)
L
IEC references
A (nH/N ) tolerance in ± %
L
core size
A250 A315 A400 A500 A630 A800 A1 000 A1 250
mm
PM50/39 5 5 7 10 10
PM62/49 3 5 5 7 10
PM74/59 3 3 5 5 7
PM87/70 3 5 5 7
PM114/93 3 3 3 5
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 17 – A and its tolerance for EC-cores (IEC 63093-11)
L
IEC references
A (nH/N ) tolerance in ± %
L
core size
A63 A80 A100 A125 A160 A200 A250 A315 A400 A500
mm
EC35 3 5 5 7 10
EC41 3 5 5 5 7
EC52 3 3 3 5 5
EC70 5 5 5 7 10
EC90 3 3 3 5 5 7
EC120 3 3 3 5 5 7
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Table 18 – A and its tolerance for EFD-cores (IEC 63093-14)
L
IEC references
A (nH/N ) tolerance in ± %
L
core size
A20 A25 A31,5 A40 A50 A63 A80 A100 A125 A160 A200 A250 A315
mm
EFD10/5/3 7 7 10 12
EFD12/6/3,5 5 5 7 10
EFD15/8/5 7 7 10 12
EFD20/10/7 5 5 7 7 10
EFD25/13/9 3 5 5 7 10
EFD30/15/9 3 5 5 7 10
NOTE To guarantee the tolerances in this table, 0,25 AQL is applied.

Bibliography
IEC 63093-2, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 2: Pot-cores for use in telecommunications, power supply, and filter applications
IEC 63093-4, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 4: RM-cores
IEC 63093-5, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 5: EP-cores and associated parts for use in inductors and transformers
IEC 63093-6, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 6: ETD-cores for use in power supplies
IEC 63093-7, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 7: EER-cores
IEC 63093-8, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 8: E-cores
IEC 63093-9, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 9: Planar cores
IEC 63093-10, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 10: PM-cores and associated parts
IEC 63093-11, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 11: EC-cores for use in power supply applications
IEC 63093-13, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 13: PQ-cores
IEC 63093-14, Ferrite cores - Guidelines on dimensions and the limits of surface irregularities -
Part 14: EFD-cores
___________
IEC 62358 ®
Edition 3.0 2026-01
INTERNATIONAL
STANDARD
Ferrite cores - Standard inductance factor for gapped cores and its tolerance

ICS 29.100.10  ISBN 978-2-8327-0980-1

CONTENTS
FOREWORD . 2
INTRODUCTION . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Measuring method . 5
5 A value and its tolerance . 5
L
5.1 General . 5
5.2 Tolerance . 5
5.3 E-core . 5
5.4 ETD-core and EER-core . 6
5.5 EP-core . 6
5.6 RM-core . 6
5.7 Pot-core . 6
5.8 PQ-core . 6
5.9 Low-profile core . 6
5.10 PM-cores . 6
5.11 EC-cores . 6
5.12 EFD-cores . 6
Bibliography . 19

Table 1 – Tolerance versus letter code . 5
Table 2 – A and its tolerance for E-cores (IEC 63093-8) . 7
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Table 3 – A and its tolerance for ETD-cores (IEC 63093-6) and EER-cores
L
(IEC 63093-7) . 8
Table 4 – A and its tolerance for EP-cores (IEC 63093-5) . 9
L
Table 5 – A and its tolerance for RM-cores (IEC 63093-4) . 10
L
Table 6 – A and its tolerance for Pot-cores (IEC 63093-2) . 10
L
Table 7 – A and its tolerance for PQ-cores (IEC 63093-13) . 11
L
Table 8 – A and its tolerance for EL-cores (IEC 63093-9) . 12
L
Table 9 – A and its tolerance for EL-I (plate)-cores (IEC 63093-9) . 12
L
Table 10 – A and its tolerance for low-profile ER-I (plate)-cores (IEC 63093-9) . 13
L
Table 11 – A and its tolerance for low-profile ER-cores (IEC 63093-9) . 14
L
Table 12 – A and its tolerance for low-profile E-I (plate)-cores (IEC 63093-9) . 15
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Table 13 – A and its tolerance for low-profile E-cores (IEC 63093-9) . 15
L
Table 14 – A and its tolerance for low-profile RM cores (IEC 63093-4) . 16
L
Table 15 – A and its tolerance for low-profile PQ-I (plate)-cores (IEC 63093-13) . 16
L
Table 16 – A and its tolerance for PM-cores (IEC 63093-10) . 17
L
Table 17 – A and its tolerance for EC-cores (IEC 63093-11) . 17
L
Table 18 – A and its tolerance for EFD-cores (IEC 63093-14) . 18
L
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Ferrite cores -
Standard inductance factor for gapped cores and its tolerance

FOREWORD
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