Trading knowledge libraryWhat One Trade Really CostsTrading Math
Trading Math
What One Trade Really Costs
A trade pays up to four costs — the spread, the commission, the slippage and the swap — and two of them never appear as a line. This paper shows you the bar a trade starts behind, what each of the four is and when it is paid, the receipt for one real trade with all four on it, and where each one is found on your platform.
Every trade starts a little behind, and the bar shows how far. At the open of 3 September 2026, one lot of the euro against the dollar — 100,000 euros — on an account with a 0.9-pip spread, a seven-dollar commission for the round trip and a 0.3-pip slip on the way in starts 1.9 pips behind. A pip is the fourth decimal place, ten dollars at one lot, so that is $19 the price has to make up before the trade is level. A fourth cost, the swap, joins the bar for every midnight the trade is held; a trade closed the same day pays none.
Four costs, four moments
The four are paid at different moments and in different places. The spread — the gap between the buying and selling price — is paid the instant the trade opens, inside the buying price. Slippage — the gap between the price clicked and the price filled — is paid at the fill, inside the price too. The commission is a line on the statement, once on the way in and once on the way out. The swap is a line at each midnight the trade is held. Two costs are lines you can read; two are inside prices and can only be found by comparing them.
