What is free margin?

What it means

Because it is calculated from equity rather than balance, free margin moves in real time with your open profit and loss. A position going against you consumes free margin even though nothing has been realised and the balance has not changed.

Why it matters

This is the number to watch rather than balance, and it is the one MetaTrader shows least prominently. A trader looking at a healthy balance figure while free margin approaches zero is one adverse move away from being unable to trade, and two away from liquidation.

What this changes in practice

For a bot, free margin is effectively the real constraint on concurrent positions. Our engine caps concurrent trades explicitly rather than relying on margin to do it, because letting margin be the limiter means the system sizes itself by whatever the broker will still permit — which is exactly the wrong moment to be taking the largest position the account allows.