What is a cross rate in forex?
A cross rate is the exchange rate between two currencies that is calculated indirectly using each currency's rate against a common third currency, most often the US dollar.
Historically, before electronic trading, dealers had to quote less common pairs (like EUR/SGD or AUD/CHF) by routing through USD.
Today many cross rates trade directly, but the underlying math is still fundamental to FX pricing, arbitrage, and risk management.