利润分为毛利和纯利。
毛利是指进价至售价的差价，不含费用的。
纯利是指毛利减去费用（人工、损耗、税费、房租等费用)
计算毛利(Gross Profit/Loss)的方法:
    * 毛利 = 净销售 (Net Sales) - 销货成本 (Cost of Goods Sold，包括工人但是不包括R&D)
    (Cost of sales (also known as cost of goods (CoGs)) includes variable costs and fixed costs directly linked to the sale, such as material costs, labor, supplier profit, shipping costs, etc. It does not include indirect fixed costs like office expenses, rent, administrative costs, etc.)
    * 净销售 = 销售 (Sales) - 销货退回与折让 (Sales Returns and Allowances)
    * 销货成本 = 期初存货(Beginning Inventory) + 购货 (Purchases) - 购货退回与折让 (Purchase Returns and Allowances) + 购货运费 (Freight-Out/Delivery Expense) - 期末存货(Ending Inventory)

计算纯利的方法:
    * 纯利(net income or profit) = 所有收入 (Revenue) - 所有支出 (Expenses)
    比较简单/粗略计算纯利也可以如下 （假设revenue只有商品销售）：
      纯利(net income or profit) = Gross profit – SGA(Selling, General and Administrative expenses) – taxes – interest.

net sales 和 Revenue 差别
     公司除了卖商品，还有其它比如卖服务，投资×××，出租房子之类的收入，同理 也会有相应的支出，所有收入减支出得到纯利；对于小公司，单独卖商品，应该都差不多

     Operating profit（经营利润）= Gross profit - SGA
     如果没有其它收入，Operating profit 和税前 net income 大致也差不多

这2个wiki做为起点还不错    

http://wiki.mbalib.com/wiki/%E6%8D%9F%E7%9B%8A%E8%A1%A8
http://en.wikipedia.org/wiki/Income_statement