Cross Rates

The term cross-rate refers to any exchange rate that is calculated from two other rates.
Although you can buy and sell any two currencies, the interbank market has historically quoted against the US Dollar as a way of reducing the number of exchange rates that need to be quoted.

Example
The GBP/SEK rate can be calculated from the following two rates:
EUR/GBP and EUR/SEK

Example
The SEK/CHF rate can be calculated from the following two rates:
USD/SEK and USD/CHF