(The full requirements are described in the ISO/IEC Directives Part 2:2011, 6.6.8.)

The decimal sign shall be a comma on the line in all language versions. If a value less than 1 is written in decimal form, the decimal sign shall be preceded by a zero.

Example: 0,001

Each group of three digits reading to the left and to the right of a decimal sign shall be separated by a small space from preceding digits or following digits respectively, except for four-digit numbers designating years.

Example:  23 456  /  2 345  /  2,345  /  2,345 6  /  2,345 67  but the year 2011

For clarity, the symbol × rather than a half-high dot (·) or asterisk (*) is used to indicate the multiplication of numbers and numerical values.

Example:  1,8 × 10^-3   (not  1,8 . 10^-3   or  1,8 · 10^-3   or   1,8 * 10^-3 )

To express values of physical quantities, Arabic numerals followed by the international symbol for the unit (see ISO 31, ISO 1000 and IEC 60027) shall be used.