How do I calculate "decremental margin"? COGS+SG&A are 40% fixed and 60% variable (as a percent of COGS+SG&A). If the company does 12% EBITDA margins, then for every $1 of Revenue, I know there are $.88 of COGS+SG&A. So, (.88*.6) = $.53 of variable costs and (.88)*(.4) = $.35 of fixed costs. So, what is the "decremental margin" for $1 loss of sales? what unit should it be expressed in?