A margin call is a warning from your broker that your account equity has fallen close to the minimum margin required to keep your open positions active. If you don't add funds or close positions to restore the required margin, the broker may automatically start closing trades — a "stop-out" — to protect both you and itself from further losses.
Margin calls are usually triggered at a set margin level percentage (e.g. 100% or 50%), which varies by broker and jurisdiction.
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Margin Calculator
Calculate the margin required to open a position at a given leverage, before you place the trade.