Conservation Capital Gains Exclusion Act of 2018 This bill amends the Internal Revenue Code to exclude from gross income, for income tax purposes, any gain from the sale of land or a qualified real property interest to a qualified organization exclusively for conservation purposes. A "qualified organization" includes certain governmental units and tax-exempt organizations. A "qualified real property interest" is any interest in real property that is: (1) the entire interest of the taxpayer, (2) a remainder interest, or (3) a restriction (granted in perpetuity) on the use which may be made of the real property.