Marginal Revenue is the extra revenue that an additional unit of product will bring a firm. It can also be described as the change in total revenue/change in number of units sold. Marginal Revenue, often abbreviated as MR, plays an important role in finding the profit-maximizing quantity, MR = MC. Marginal Revenue is a concept important in basic microeconomics.
Marginal Revenue (MR) is equal to the change in total revenue over the change in quantity when the change in quantity is equal to one unit (or the change in output in the bracket where the change in revenue has occurred)
MR=change in TR / change in qty (where change in qty = 1)