Coat weight is normally specified as dry weight in g/m², and it is the number that connects performance to cost.
Too little and the coating cannot deliver its function — barrier, gloss, protection or opacity all scale with thickness. Too much and you are wasting material, risking incomplete drying or cure through the film depth, and possibly causing defects like cracking or poor adhesion from shrinkage stress.
In UV curing there is a specific constraint: thicker films need more energy to cure through, and in pigmented systems the top of the film absorbs UV that never reaches the bottom. Undercure at the substrate interface is a common cause of adhesion failure in heavy UV films.
Dry coat weight relates to wet application by the solids content, which is why the two numbers are always quoted together.