The platform does not ask your opinion. At 2:14pm it simply closes your position, at the worst price of the day, and the log entry reads: stop out. Thousands of traders meet the margin system for the first time exactly this way, mid-loss, confused, and convinced the broker did something underhanded. It did not. It followed rules that were visible on the screen the entire time, in four numbers most beginners never learn to read. Learn them once and a forced liquidation should never happen to you.
The deposit that gets reserved
Margin is not a fee and not a cost. It is a security deposit. Open one lot of EURUSD, $100,000 of notional exposure, on an account with 1:30 leverage, and the broker sets aside $3,333 of your money as collateral for as long as the position lives. You cannot spend it on other positions, but it is still yours: close the trade and every cent of it returns instantly. What actually leaves your account is the spread and any floating loss. Margin just sits there, reserved, guaranteeing that you can cover what the position might lose.
The four numbers on your platform
- Balance: your account with all closed trades settled. Open positions do not touch it. Example: $10,000.
- Equity: balance plus the floating P&L of open positions. One lot of EURUSD running 50 pips against you means equity of $10,000 minus $500, so $9,500. Equity is the truth; balance is history.
- Margin: the total reserved for open positions. The one-lot example at 1:30 reserves $3,333.
- Free margin: equity minus margin, here $9,500 minus $3,333, so $6,167. This is what is available for opening anything new.
- Margin level: equity divided by margin, times 100. Here 9,500 / 3,333 gives 285%. This single percentage is what the broker's enforcement machinery watches.
The cascade, with numbers
Follow one bad trade all the way down. A $10,000 account buys one lot of EURUSD at 1:30 leverage, margin $3,333, no stop loss. The trade goes wrong by 300 pips: floating loss $3,000, equity $7,000, margin level 210%. That is uncomfortable, but nothing happens. Another 300 pips: equity $4,000, margin level 120%. At 100%, equity $3,333, the margin call arrives. On modern platforms this is not a phone call but a state: you cannot open new positions, and the platform is formally warning you. The market keeps going. When margin level reaches the stop-out threshold, commonly 50%, equity $1,667 here, the platform force-closes the position at market, no confirmation, no appeal. Total damage: $8,333, or 83% of the account, on a single unstopped lot that needed to travel about 660 pips. The slide was gradual, visible on screen the entire way down, and entirely preventable.
Free margin and the temptation to add
Free margin answers one question: can another position be opened? With $6,167 free, the platform will happily let you add more lots. This is where accounts compound their first mistake, adding to losers or stacking correlated trades because the free margin made it feel affordable. Free margin measures capacity, not wisdom. A cleaner personal rule: if total margin ever exceeds 20 to 30% of equity on an intraday account, your positions are far beyond anything a 1% risk rule would produce, and the margin math has become a countdown rather than a formality.
Never meeting the machinery
The entire cascade has one root cause: position size out of proportion to the account, running without a stop. Both are solved by the same habit. Size every trade so the stop loss costs 1% of equity, and the numbers become boring: 0.40 lots with a 25 pip stop can lose $100, which moves equity from $10,000 to $9,900 and leaves the margin level in the many hundreds of percent. A trader operating this way can go an entire career without ever seeing a margin call, and that is precisely the goal. Margin mechanics are like the airbag specifications of your car: worth understanding once, and best never experienced firsthand.