How long is that?

As is the convention in the Construction Building and Engineering industries in Australia, dimensions of glass are usually stated in millimetres (mm). This differs from the cooking clothing domestic and Police Wanted Poster situations where centimetres (cm) is the norm.

There are two reasons for this — clarity and avoiding confusion. Millimetre is a sufficiently small unit of measurement that something smaller will rarely be called for. To illustrate, 215mm is a perfectly clear dimension and requires no suffix to define it. On the other hand, 21.5 cm does require the measurement unit to be specified, as well as a decimal point to provide for small dimensions.

A decimal point is a very small point indeed: so small in fact that it could easily be mistaken in a handwritten document for a fly spot. Our 21.5cm could be easily read as 215cm

Both large and small dimensions can be stated with equal clarity in millimetres without confusion. A piece of glass can be 215 x 180 x 3. All mm’s, nothing stated, no confusion. A block of land can be 64500 long. That’s 64.5 metres, but no problem with the unit of measure nor the decimal point.

There can be some in art glass supply outlets who aren’t aware of this convention, so it may be best if one follows the convention but still specifies mm as the unit of measurement when ordering.

NOTE. mm and cm are lower case, not upper case: not MM or CM. 

Imperial vs metric

Whilst it is gradually changing, much American literature uses Imperial measure: feet and inches.The following may help in converting that into our language: