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Updated on 2023-09-19
Typographic and editorial rules

Numbers

Estimated reading: 2 minutes

Each group of three digits reading to the left and to the right of a decimal sign is separated by a thin space [1/4 Em space] from preceding digits or following digits respectively

 

Exceptions: years, numbers used in references

This rule does not concern binary or hexadecimal values

Examples1

1 000 000
59 531,66
1,618 033 988 75
2019 [current year]
IEC 62501

Note

In Word for Office 365,
Insert>Symbol>More Symbols>Special Characters>1/4 Em Space
alternatively, you can assign your own shortcut keygo.iec.ch/iecsgfont

The decimal separator is a comma [not a dot]

Examples1

8,187 million

All numbers from one to nine shall be spelled out. From 10 on, numbers shall be written in figures

Exceptions:

  • when a sentence starts with a number it shall be spelled out, except for years
  • numbers in a list shall all be in figures
  • numbers in a reference, an address, etc. shall be written in figures
Examples1

Twenty people are attending
Over 20 people are attending
2019 is a challenging year
this may occur 8, 9 or even 10 times
IEC is located at 3 rue de Varembé
as specified in clause 5

The minus sign is En dash [–] not hyphen [-]

Examples1

–6 °C

Note

In Word for Office 365,
Insert>Symbol>More Symbols>Special Characters>En Dash, or
keyboard shortcut for En dash: Ctrl+Num Lock+-go.iec.ch/iecsgfont

There is no space between a mathematical symbol and a number when it is a value

Use a space before and after a mathematical symbol in formulae

Examples1

>5
9 > 8
4 – 2

Exception

These rules do not apply to reports issued in their entirety by the Finance and Accounting departmentgo.iec.ch/iecsgfont

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