The following convensions (rules) should be strictly followed
while writing SI units.
i. While writing a
unit, only its singular form is used.
For example, the
mass of any substance should be written as kg not as kgs.
Distances
should be expressed in km not in kms,
e.g., ten kilogram
is written as
10
kg 10
kgs
(correct) (incorrect)
ii. The
abbreviation of any unit does not have full stop (.) at the end, unless it
appears at the end of a sentence. Therefore, no full stop is placed either in
between or at the end of the symbol of the unit.
For example,
kg kg. cm cm.
(correct) (incorrect) (correct) (incorrect)
iii. One space is
left between the last digit of a numeral and the symbol of the unit.
For example,
10
m 10m 5
g 5g
(correct)
(incorrect) (correct) (incorrect)
iv. Words and
Symbols should not be mixed.
For example,
Kilogram per cubic metre kg/m3 kilogram/m3 kg
per cubic metre
(correct) (correct) (incorrect) (incorrect)
v. With numerals,
the symbol of the unit should be written.
For example,
100
cm one
hundred
cm 100
centimetres
(correct) (incorrect) (incorrect)
vi. The names of
the units derived from people’s names are written in small letters.
For example,
the unit named after Joule is written as joule, (symbol: J).
The unit of
force named after newton is written as newton, (symbol: N).
vii. The sign of degree (°) is not
written when Kelvin scale is employed.
For example, temperature of 273 kelvin is written as 273 K and
not 273°K.
273
K 273°K
(correct) (incorrect)
