Currency pairs (symbols)

A currency pair, often called a symbol expresses the value of one currency in units of another, written as BASE/QUOTE. For example, EUR/USD prices the euro in US dollars.

Currency pairs are used extensively when making FX trades or cross-border payments.

General principles

• Two currencies separated by one slash. A currency pair has a base currency, a slash, and a quote currency. Example: EUR/USD.
• ISO 4217 codes. Write each currency as its three-letter ISO 4217 alphabetic code in uppercase.
• The base currency is always one unit. The rate is the amount of quote currency that buys one unit of base currency. EUR/USD at 1.0850 means 1 EUR = 1.0850 USD.
• Order sets direction. EUR/USD and USD/EUR are different pairs. Their rates are inverses of each other, before spread.
• Market convention sets the order. The base currency is the first of EUR, GBP, AUD, NZD, USD, then any other currency. This is a market convention, rather than an ISO rule.
• Same format as FIX. The CCY1/CCY2 format with ISO currency codes is the one the FIX Symbol field uses for foreign exchange.

How to build a currency pair

1. Look up the ISO 4217 alphabetic code of each currency.
2. Rank both codes with the convention: EUR, GBP, AUD, NZD, USD, then all other currencies.
3. Put the higher-ranked code first. This is the base currency.
4. Put the other code second. This is the quote currency.

Examples of valid currency pairs