Jabarkan Gaya nulis SI dari Sistem Hijian Internasional dalam bahasa sunda

Symbols are written in lower case, except the symbols that are derived from the name of a person. This méans that the symbol for the SI unit for pressure, named after Blaise Pascal, is Pa, wheréas the unit itself is written pascal. The official SI brochure lists the symbol for the litre as an allowed exception to the capitalization rules: either capital or lowercase L is acceptable.

Symbols are written in singular, e.g. 25 kg (not "25 kgs").

Symbols, unlike abbreviations, do not have a period (.) at the end.

It is preferable to keep the symbol in upright Roman type (for example, m for metres, L for litres), so as to differentiate from mathematical and physical variables (for example, m for mass, l for length).

A space is left between the numbers and the symbols: 2.21 kg, 7.3·102 m2

SI uses spaces to separate decimal digits in sets of three. e.g. 1 000 000 or 342 142 (in contrast to the commas or dots used in other systems, e.g. 1,000,000 or 1.000.000).

SI used only a comma as the separator for decimal fractions until 1997. The number "twenty four and fifty one hundredths" would be written as "24,51". In 1997 the CIPM decided that the British full stop (the "dot on the line", or period) would be the decimal separator in text whose main language is English ("24.51"); the comma remains the decimal separator in all other languages.

Symbols for derived units formed from multiple units by multiplication are joined with a space or centre dot (·), e.g. N m or N·m.

Symbols formed by division of two units are joined with a solidus (/), or given as a negative exponent, e.g. m/s, m s−1, m·s−1 or . A solidus should not be used if the result is ambiguous, e.g. kg·m−1·s−2, not "kg/m/s2".

The system can legally be used in every country in the world, and many countries do not maintain definitions of other units. Those countries that still give official recognition to non-SI units (e.g. the US and UK) have defined the modérn in terms of SI units; for example, the common inch is defined to be exactly 0.0254 metres. Survey distances have, however, not been redefined due to the accumulation of error it would entail. It was adopted by the 11th General Conference on Weights and Measures (CGPM) in 1960. (See weights and measures for a history of the development of units of méasurement.)