Accounting profit is the difference between price and the costs of bringing a chemical to market.The following terms are usually used:
Profit before tax（稅前利潤）is the sales of the firm less costs such as wages，rent，fuel，raw materials，interest on loans and depreciation
Gross profit（毛利）is profit before selling，general and administrative costs，like depreciation and interest；it is the sales less direct cost of goods（or services）sold
Net profit after tax（淨利潤）is after the deduction of either corporate tax（for a company）or income tax（for an individual)
Operating profit（營業利潤），also known as earning before interest and tax（EBIT，息稅前利潤），is a measure of a company's earning power from ongoing operations，equal to earnings before the deduction of interest payments and income taxes
To accountants，economic profit（EP，經濟利潤）is a single-period metric to determine the value created by a company in one period，usually a year.
During the economic evaluation of a chemical engineering design project，the first stage in evaluating the profitability of a proposed new product is to compare the total cost of the product（for example，per tonne produced）with the current market price.It is also necessary to estimate future demand for the product，and to determine the trend in the selling price over several previous years.It is also necessary to estimate the number of years that the product can be sold at a satisfactory profit，this is more useful than estimating the possible operating life of a plant.It is suggested that a large chemical organization will not invest in a new process unless it is possible to sell the product for less than half the current market price.
Two other measures that can be used to evaluate the profitability of a product are the return on investment and the payback period（回收期）.The return on investment（ROI，投資回報率）is the expected profit divided by the total capital invested，expressed as a percentage return.It must be clearly stated whether the profit is based on pre-tax or after-tax earnings.The after-tax ROI is compared with the earnings that could be achieved by an alternative investment，e.g.，capital bonds.An after-tax ROI of at least 15%～20% is usually expected（or 30%～40% pre-tax ROI)，assuming that the project is not particularly risky.