The micrometre (American spelling micrometer) is a unit of length and is a multiple of the SI unit metre. It uses the symbol μm.
It represents one millionth of a metre and is also known by its previously depreciated name micron.
In the US, the term 'micron' helped distinguish the unit name from the device 'micrometer' but the International System of Units (SI) discontinued this term in favour of micrometre as the prefix system required the use of the Greek symbol 'μ' which invoked the factor x10−6.
The centimetre is a unit of length and is a multiple of the metre; an SI derived unit. It has the symbol cm.
A centimetre is equal to 0.01m. It is also ≈ 0.3937in.
Centimetres are used in maps to scale up conversions to real world measurements.