You need to subtract the opening price from the closing price of the transaction, multiply it by the number of lots and the contract size, and subtract the commission. Say you bought 3 lots of Brent oil (UKOIL) at 122.50 and are now selling it at 124.00. Your profit will bet: (124.00 (closing price) – 122.50 (opening price) x 3 (lot) x 1000 (contract size) – $30 (commission) = $4,470.
To calculate your profit on a Bitcoin trade (BTCUSD), subtract the opening price from the closing price of the trade, then multiply the result by the number of lots and the size of the contract and subtract the commission. For example, if you bought 0.5 lot of Bitcoin at $7,000 and sold it at $9,350 with a 1% commission. Your profit will be: ($9,350 (closing price) – $7,000 (closing price)) x 0.5 (lot) x 1 (contract size) – $35 (commission) = $1,140.