This document provides guidelines for estimating costs for process plant design projects. It covers estimating capital investment costs, which include the costs of purchased equipment, installation, piping, instrumentation, buildings and other facilities. It also covers estimating total production costs, which include operating labor, utilities and other expenses. The document provides methods and factors for conducting economic analysis of projects, including calculations for depreciation, taxes, cash flow, net present value, return on investment and payout period. It includes examples of applying the cost estimating methods to sample process plants such as a refinery unit, ethylene plant and ammonia plant.