Bitcoin Exchange RatesAs of today, the only exchange that has enough liquidity and tight spreads to pull real time rates is BTC/USD.
To calculate the exchange rate for US Dollars, we pull up-to-the-minute BID prices from three exchanges. We take the 2 that are closest together and toss out the third, so that a bad feed from one exchange will not affect our calculation. Of the 2 rates that remain, Bit-Pay uses the highest BID price as our exchange rate.
To calculate the exchange rate for currencies other than the US Dollar, we use the USD rate described above and multiply it by the daily ECB ForEx rates compared to the US Dollar.