汇率是两国货币之间的比率，要计算这个比率，首先得确定用哪个国家货币作计算标准。目前，国际汇市上标价方式有两种：直接标价（direct quotations）与间接标价(indirect quotations)。

除了英国、美国、澳大利亚、新西兰等之外，世界上绝大多数国家，包括中国在内，都采用直接标价法来表示汇率。这种标价方法用外国货币作计算标准。一般是1个单位或100个单位的外币能够折合多少本国货币，本国货币的汇率就是多少。

Direct Quote vs. Indirect Quote

There are two ways to quote a currency pair, either directly or indirectly. A direct quote is simply a currency pair in which the domestic currency is the base currency; while an indirect quote, is a currency pair where the domestic currency is the quoted currency. So if you were looking at the Canadian dollar as the domestic currency and U.S. dollar as the foreign currency, a direct quote would be CAD/USD, while an indirect quote would be USD/CAD. The direct quote varies the foreign currency, and the quoted, or domestic currency, remains fixed at one unit. In the indirect quote, on the other hand, the domestic currency is variable and the foreign currency is fixed at one unit.

For example, if Canada is the domestic currency, a direct quote would be 0.85 CAD/USD, which means with C$1, you can purchase US$0.85. The indirect quote for this would be the inverse (1/0.85), which is 1.18 USD/CAD and means that USD$1 will purchase C$1.18.

In the Forex spot market, most currencies are traded against the U.S. dollar, and the U.S. dollar is frequently the base currency in the currency pair. This would apply to the above USD/JPY currency pair, which indicates that US$1 is equal to 119.50 Japanese yen.

However, not all currencies have the U.S. dollar as the base. The Queen's currencies - those currencies that historically have had a tie with Britain, such as the British pound, Australian Dollar and New Zealand dollar - are all quoted as the base currency against the U.S. dollar. The Euro, which is relatively new, is quoted the same way as well. This is why the EUR/USD quote is given as 1.55, for example, because it means that one euro is the equivalent of 1.55 U.S. dollars.

Most currency exchange rates are quoted out to four digits after the decimal place, with the exception of the Japanese yen (JPY), which is quoted out to two decimal places.

为甚麼外国英文网站跟这解释不一样的?