The mid-market rate is an exchange rate unlike any other. It’s the real one.
In the world’s currency markets, traders define the rates at which they are willing to “buy” or “sell” a specific currency. The mid-market rate is simply the midpoint between demand and supply for a currency, and because of that, it changes all the time.
But that’s as technical as you need to get. The most important thing to know is that the mid-market rate is considered the fairest exchange rate possible.
The mid-market rate isn’t a secret either. Its the rate you will find on independent sources such as Google, XE and Yahoo Finance.