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Trading Math
How to Calculate the Margin a Trade Needs
The margin a trade needs is its whole value divided by the leverage. This paper shows you the sum on one real trade, the same trade at three leverages, the same sum on gold and an index where the contract size differs, why margin is a hold and not a cost, and where the platform shows its own answer a second after the trade opens.
Every trade has a full value, and the margin is a slice of it. A lot is 100,000 units of the currency on the left, so one lot of the euro against the dollar is 100,000 euros, and at the open of 3 September 2026, 1.15872, that is 115,872 dollars. Leverage is the ratio between that full value and the part of it the broker asks the account to hold: at one-to-one-hundred the broker holds back one hundredth, $1,158.72, and lends the rest. Lots times 100,000 times the price, divided by the leverage. That hold is the margin.
The same lot at three leverages
Change the leverage and only the divisor changes. The same one lot, the same 115,872 dollars of euros, holds back $3,862.40 at one-to-thirty, $1,158.72 at one-to-one-hundred and $231.74 at one-to-five-hundred. The trade is identical in every case, and so is what it makes or loses — on 3 September, $387 at each of the three ratios. Leverage changes how much of the account is held while the trade is open, and nothing else about the trade.
On another symbol the sum is the same with one substitution: the contract size comes from that symbol's specification page instead of being 100,000. A lot of gold is 100 ounces, so a tenth of a lot is ten ounces, worth $43,960.90 at the 8 September 2026 close of 4,396.09 and holding back $439.61 at one-to-one-hundred. A lot of the Nasdaq is one contract, worth $29,602.23 at its close and holding back $296.02. Lots times contract size times price, divided by the leverage, on every sheet.
