I, Dr Victoria Anne Coleman, Chief Metrologist, National Measurement Institute, make these Guidelines.
Dated 9 March 2026
Dr Victoria Anne Coleman
Chief Metrologist
Contents
1 Name
2 Commencement
3 Authority
4 Schedules
5 Definitions
6 Objects
7 Physical quantities
8 Combining Australian legal units of measurement
9 Combining Australian legal unit of measurement and prescribed SI prefix
10 Australian legal units of measurement that must not be combined with prefixes
11 Australian legal units of measurement that may only be combined with prefixes that form multiples of the unit
12 Expression of Australian legal units of measurement
Schedule 1—Repeals
1 The whole of the instrument
1 Name
This instrument is the National Measurement Guidelines 2026.
2 Commencement
Each provision of this instrument specified in column 1 of the table commences, or is taken to have commenced, in accordance with column 2 of the table. Any other statement in column 2 has effect according to its terms.
Commencement information
Column 1 Column 2 Column 3
Provisions Commencement Date/Details
The whole of this instrument The day after this instrument is registered.
Note: This table relates only to the provisions of this instrument as originally made. It will not be amended to deal with any later amendments of this instrument.
Any information in column 3 of the table is not part of this instrument. Information may be inserted in this column, or information in it may be edited, in any published version of this instrument.
3 Authority
This instrument is made under section 7B of the National Measurement Act 1960.
4 Schedules
Each instrument that is specified in a Schedule to this instrument is amended or repealed as set out in the applicable items in the Schedule concerned, and any other item in a Schedule to this instrument has effect according to its terms.
5 Definitions
In these Guidelines:
Act means the National Measurement Act 1960.
Product Symbol means a symbol used to indicate the product of 2 or more Australian legal units of measurement.
Regulations mean the National Measurement Regulations 1999.
SI Prefix means a prefix mentioned in Schedule 3 of the Regulations.
6 Objects
These Guidelines govern the way in which Australian legal units of measurement may be combined:
(a) to produce an Australian legal unit of measurement; and
(b) with prefixes to produce Australian legal units of measurement.
7 Physical quantities
Australian legal units of measurement may be formed only for the physical quantities as prescribed under the Regulations.
8 Combining Australian legal units of measurement
An Australian legal unit of measurement for a physical quantity may be formed by combining Australian legal units of measurement according to the mathematical relations linking the corresponding physical quantities.
The resulting Australian legal unit of measurement may be represented by using a name or symbol that is itself formed from derived units.
Example pascal (pressure in newtons per square metre): Pa = N/m2.
9 Combining Australian legal unit of measurement and prescribed SI prefix
A decimal multiple, or submultiple, of an Australian legal unit of measurement must be formed by using a single SI Prefix.
Example Nanometre: 1 nm or 1 x 10-9 m, but not 1 mµm.
Subsection 9(1) of these Guidelines does not apply to kilogram.
Example 10-6 kg or 1 mg, but not μkg.
Note Kilogram is an SI base unit of measurement: see Regulations, Sch 1, item 1.1.
An additional derived unit of measurement, mentioned in Part 4 of Schedule 1 to the Regulations, may be combined with another Australian legal unit of measurement to form an Australian legal unit of measurement.
Note An exponent associated with a symbol for an Australian legal unit of measurement indicates that the multiple, or submultiple, of the unit is raised to the power expressed by the exponent.
The combination of the unit and a prefix may be combined with other Australian legal unit of measurement symbols to form the symbol for a compound unit that is an Australian legal unit of measurement.
Example Speed in kilometres per hour: km/h.
10 Australian legal units of measurement that must not be combined with prefixes
The following Australian legal units of measurement must not be combined with SI prefixes:
kilogram
minute
hour
day
decibel
inch
foot
hectare
ounce
foot/minute
degree
minute
second of arc
radian
steradian
degree Celsius
A decimal multiple or sub-multiple of kilogram must be formed by attaching a prefix to gram.
Note For historical reasons, kilogram already contains a prefix.
11 Australian legal units of measurement that may only be combined with prefixes that form multiples of the unit
Tonne may be combined only with an SI Prefix that gives a decimal multiple of tonne.
Example kilotonne, but not millitonne.
12 Expression of Australian legal units of measurement
Names and symbols of Australian legal units of measurement must not be used together in the same expression.
Example km/h, but not kilometre/h.
An adjective or sign must not be added to the name or symbol of an Australian legal unit of measurement.
Example Wa cannot be used as the unit of acoustic power.
The symbol for an SI Prefix must be placed immediately before the symbol of the Australian legal unit of measurement to which it refers, without an intermediate space.
Examples
1 milliwatt: mW
2 kilometre: km
3 gigatonne: Gt
4 megajoule: MJ
For a decimal multiple or submultiple of an Australian unit of measurement that is expressed as a fraction, an SI prefix:
may precede the Australian legal unit of measurement in the numerator or the denominator, or both if there is no other way to form an unambiguous expression; and
should precede the Australian legal unit of measurement in the numerator.
Examples
1 km/s, but not mm/s or m/ms
2 mm/s, but not m/ks
Only a single SI Prefix may be used to form a multiple of a derived Australian legal unit of measurement.
The product symbol is:
a dot (·);
if the resulting expression is unambiguous — a full stop (.); or
if the symbol for an Australian legal unit of measurement is not the same as an SI prefix — a space.
Example Thermal resistivity (metre kelvin per watt): m·K/W, not m K/W which may be confused with millikelvin per watt (mK/W).
The product symbol must be used only with symbols that represent Australian legal units of measurement.
Example N·m or N m, but not Newton·metre
An Australian legal unit of measurement derived from the division of 2 other Australian legal units of measurement may be expressed using an oblique stroke (/), a horizontal line or a negative exponent to produce an unambiguous expression.
The oblique stroke must not be repeated on a line unless ambiguity is avoided by the use of parentheses. In a complex expression, negative exponents or parentheses must be used.
A space must be left after the numerical value of an Australian legal unit of measurement and before the name or symbol of the unit of measurement.
Examples
1 22 m, but not 22m
2 27 volts, but not 27volts
3 15 °C, but not 15°C
Note 1 When expressing temperature in degrees Celsius, a space must not be left between the symbol for degrees and the symbol for Celsius. See example 3.
However, subsection 12(10) of these Guidelines does not apply when expressing the numerical values and the symbols for degrees, minutes and seconds of: