Gross National Product [GNP] is the gross value of all the final products without deducting the depreciation of fixed capital. It is the total of market value of final goods and services produced in a years. 
Net National Product [NNP] is the value of net output in an economy during a period of one year. The net national product is calculated by deducting depreciation from the gross national product.NNP = GNP - Depreciation