You bought 2 lots of EURGBP at price 0.8648, in few days, the price goes up and you close your position at price 0.8702. The resulting profit will be as follows:
Note: the exchange rate for GBPUSD at the time of closing the order is 1.5287
Profit = (Bid Price – Ask Price) X Contract Size X Number of Lots X Exchange Rate (USD)
= (0.8702 – 0.8648) X 100,000 X 2 X Exchange Rate for (GBPUSD) = 0.0054 X 200,000 X 1.5287 = 1,650.996 USD
And as you can trade in spot forex, so you can buy or sell futures contracts of currencies in the futures market for delivery on a specified future date.
Futures contracts for currencies are all quoted in US Dollars. Therefore, your profits will be directly calculated in USD according to the following equation:
For Futures Currencies:
Profit/Loss = (Bid Price – Ask Price) X Contract Size X Number of Contracts
Profit & Loss Calculation for Metals
As for precious metals, gold and silver prices are in USD, the profits/ losses are directly calculated in USD according to the simple equation below:
For Precious Metals:
Profit/Loss = (Bid Price – Ask Price) X Contract Size X Number of Lots
Same equation applies to futures contracts of precious metals as they have the same contract size and denominated in USD as well.
Note that the contract size of 1 standard lot of sliver is 5,000 ounces, and for gold is 100 ounces.