Marking to Market

Once a trader knows their average rate, it is relatively easy to calculate the current value of their open position, in terms of profit or loss. It is calculated by comparing the average rate we previously calculated to the current market price on the trading screen. This is called marking to market or revaluing.
When spot traders square their position, they can calculate their net profit or loss by comparing the average rate of their trades to the rate at which they close their position. Nowadays, this is generally done electronically.
In our example, the FX trader has a long CNY 10 million position and a short JPY 164,387,500 position.