Portfolio value is calculated separately for each margin account by adding the account balance to the profit or loss from open positions held in the account:
Portfolio Value = Margin Account Balance + Profit or Loss from Open Positions
This calculation happens in real-time and you can view this on the Balances panel as the market moves.
We calculate the profit or loss from open positions based on our estimate of the current price of the instrument:
For inverse Futures, profit or loss is calculated as:
Profit or Loss from Open Positions = ( 1 / Entry Price - 1 / Current Price ) * Position Size
For vanilla Futures, profit or loss is calculated as:
Profit or Loss from Open Positions = ( Current Price - Entry Price ) * Position Size
We continuously update our estimates of current instrument prices based on current spot prices (as given by our real-time indices), and our estimate of the current forward premium or discount:
Current Price = Spot Price + Current Forward Premium or Discount
We calculate the current forward premium or discount as the percentage deviation of the instrument's current mid price from the spot price. The maximum permissible premium or discount is capped at 1% for Futures with 1 day to maturity and 20% for Futures with 210 days to maturity and is linearly interpolated in between (perpetual futures, which do not expire, have a premium cap of 1%).
Note that our estimate of current instrument prices is used only for margin management and does not affect your actual profit or loss once a position is closed out or settled.