利潤的計算

Your calculation is right for simple gross profit ratio.

So, it is the definition of your Profit. There may be a gross profit, a profit before selling and distribution expenses. a profit before general and administrative expenses, a profit before tax,

利潤=買出價減去成本價
成本價=入貨價 + 實際支出(如運輸,儲存等....) + 管理人支出(人工,利息支出等....)
所以 $5.00-$3.00/ $5.00 x100% 是錯的計法，要計算利潤必須知到其它的支出才可計算出來。