The essence of marginal profit and the formula for calculating its rate are shown. A technique is given for deriving a formula for calculating the marginal profit depending on the level of crop yields. It is emphasized that ceteris paribus, as the yield increases, the value of marginal profit at a constant price for products is equal to the value of cost reduction. On the example of a specific agricultural enterprise, calculations of the marginal profit of marketable products for three leading crops are given.The results of calculations of the relationship between yield and marginal profit arepresented in the graphs. The article concludes that as land productivity grows, both the absolute and relative value of marginal profit decreases. The methodology for calculating the marginal profit makes it possible to identify the available reserves for increasing the efficiency of marketable products for each of its types.