My dad who just retired at age 83 from the Australian building industry explained it to me that plans and measurements will use either metres or millimetres, bu

My dad who just retired at age 83 from the Australian building industry explained it to me that plans and measurements will use either metres or millimetres, but never centimetres. The thinking being you can usually figure out which is which for any given number, but you add centimetres into the mix then it becomes much more ambiguous.