What does SMT material code 0603 0805 mean?

This number refers to the size of the material, and the metric and English codes are different.

The first two digits represent the length of the material; The last two digits represent the width of the material,

For example, metric system 0603 indicates that the length of the assembly is 0.6 mm and the width is 0.3 mm..

British system 0603 indicates that the length of the assembly is 0.06 inch and the width is 0.03 inch.