The picture above show the SMT component sizes.
Normally component sizes were used with imperial units, like 1206, 0805 etc. The problem occur when after 0201 (20 x 10 mils) new component was introduced with 10 x 5 mils the new name 01005 didn’t sound so well. So most SMT machine manufacturers switched to metric system and all parameters in Samsung and Sony machines for instance are in metric units.
My first confusion was when I decided to buy Sony machine in the specs I read: can place components with size from 0603 up to 40×40 mm. I told myself WTF? So expensive machine and works just with 0603 components????
But then the Sony technical support explained to me that 0603 is metric and corresponds to 0201 imperial units. Later when Sony closed their business we were looking aroung for our next machine and reading Samsnug specs:
We already know that 0603 is metric and corresponds to 0201 imperial.
So the bottom line is when you speak for SMT components with size 0402 or 0603 always mention in what units you are talking or confusions could be possible😉