Current Price (USD) for base currencies is calculated from the current bids on these pairs in real time. Current Price (USD) for alt coins is calculated using cross bids.
The formula for alt coins
Current Price (USD) = Highest current bid to base crypto currency * Current Price (USD) of base cryptocurrency
Example
A trader buys 1 ETC for 0.001130 BTC. The current bid for BTC/USD is $4296.76.
0.001130 * 4296.76 = $4.85
Current Price (USD) is $4.85
Where can you see Current Price (USD)
1. Dashboard - Portfolio/Trading Account.
Here you will find the Current Price $ for each of your assets:
2. Exchange - Portfolio.
A table similar to the one in your Dashboard - allowing you to monitor the current prices for your assets whilst trading.
3. Exchange - Order Book.
Here you can see the Current Price $ for any asset along with the assets corresponding base currency amount.