ISO 80000-1

ISO 80000-1:2009 is a standard describing scientific and mathematical quantities and their units. The standard, whose full name is Quantities and units Part 1: General was developed by the International Organization for Standardization (ISO), superseding ISO 31-0. It provides general information concerning quantities and units and their symbols, especially the International System of Quantities and the International System of Units, and defines these quantities and units. It is a part of a group of standards called ISO/IEC 80000.

The standard is divided into the following chapters:

ISO 80000-1 gives "general information and definitions concerning quantities, systems of quantities, units, quantity and unit symbols, and coherent unit systems, especially the International System of Quantities, ISQ, and the International System of Units, SI."

The standard includes the following definitions.

The special choice of base quantities and quantity equations, including multipliers, given in ISO 80000 and IEC 80000 defines the International System of Quantities, denoted “ISQ” in all languages. Derived quantities can be defined in terms of the base units by quantity equations. There are seven base quantities in the ISQ: length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity.

Section 6.5 of the standard describes the International System of Units including SI prefixes and IEC binary prefixes kibi- to yobi-.

Section 7.3.2 states that the decimal mark is either a comma or a point on the line and further states that whichever decimal mark is used, that same mark should be consistently used. This is in agreement with prior ISO standards and revisions, notably resolution 10 of the 22nd CGPM, 2003.

According to Annex A, "[t]he logarithm of the ratio of a quantity, Q, and a reference value of that quantity, Q₀, is called a level". For example L_P = ln(P/P₀) is the level of a power quantity P.

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