P

Alphabetical index

pascal

Unit of measurement of pressure, symbol: Pa.

“per” or “divided by”

The symbol for “per” is /
e.g. 50 km/h not 50 kph.

peta

Prefix of multiple 10¹⁵, symbol: P.

pico

Prefix for a subdivision of 10^-12, symbol: p.

plurals

Symbols are never pluralised.
e.g. 25 kg not 25 kgs.

precision

A number normally implies its precision; thus 14 m is likely to mean a distance between 13.5 m and 14.5 m. When converting, do not make the converted figure more precise than is implied in the original e.g. 20 000 feet becomes 6000 m not 6096 m.

prefixes

A prefix is a way of multiplying or dividing a unit by 10, 100, 1000, etc.

punctuation

Do not put a full stop (period) after a unit symbol, except at the end of a sentence.

Leave a space between the number and the unit where possible.