The following are the rules and conventions for writing SI Units and their symbols:
- The units named after scientists are not written with an initial capital letter.
Example: newton, henry, ampere and watt.
- The symbols of the units named after scientists should be written by the initial capital letter.
Example: N for newton, H for henry, A for ampere and W for watt.
- Small letters are used as symbols for units not derived from a proper noun.
Example: m for metre, kg for kilogram.
- No full stop or other punctuation marks should be used within or at the end of symbols.
Example: 5 m, and not as 5 m. or 5.m
- The symbols of the units are not expressed in plural form.
Example: 100 kg, not as 100 kgs.
- When the temperature is expressed in kelvin, the degree sign is omitted.
Example: 383 K, not as 383° K (If expressed in celsius scale, degree sign should be included, e.g. 100 °C, not as 100 C and 108 °F, not as 108 F).
- Use of solidus (/) is recommended for indicating a division of one unit symbol by another unit symbol. Not more than one solidus is used.
Example: or m/s. J/K/mol should be
- The number and units should be separated by a space.
Example: 15 not as 15
- Accepted symbols alone should be used.
Example: Ampere should not be written as amp, and second should not be written as sec
- The numerical values of physical quantities should be written in scientific form.
Example: The density of mercury should be written as , not as