計算DSO的三種方法：（1）期間平均法。（2）倒推法。（3）賬齡分類法
（1）期間平均法。 這是最普遍的方法，但也是誤差最大的計算方式。
計算的期間可以是三個 月、半年或者一年。
DSO=期未應收賬款餘額/這一時期的銷售額×這一時期的天數
（2）倒推法。
倒推法是以最近的一個月為開始，用總的應收賬款減去的總天數，總天數即為DSO。
這種DSO的計算方法注重最近的賬款回收業績，而非全年或半年的業績。
這種方法是使用率最高的一種方法。
（3）賬齡分類法 這種方法綜合考慮了賒銷和賬齡的關係。
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What Does Days Sales Outstanding - DSO Mean?
A measure of the average number of days that a company takes to collect revenue after a sale has been made. A low DSO number means that it takes a company fewer days to collect its accounts receivable. A high DSO number shows that a company is selling its product to customers on credit and taking longer to collect money.
Days sales outstanding is calculated as:
Investopedia explains Days Sales Outstanding - DSO
Due to the high importance of cash in running a business, it is in a company's best interest to collect outstanding receivables as quickly as possible. By quickly turning sales into cash, a company has the chance to put the cash to use again - ideally, to reinvest and make more sales. The DSO can be used to determine whether a company is trying to disguise weak sales, or is generally being ineffective at bringing money in. For most businesses, DSO is looked at either quarterly or annually.
