The deposit required to open or maintain a position. Margin can be either "free" or "used". Used margin is that amount which is being used to maintain an open position, whereas free margin is the amount available to open new positions. With a $1,000 margin balance in your account and a 1% margin requirement to open a position, you can buy or sell a position worth up to a notional $100,000. This allows a trader to leverage his account by up to 100 times or a leverage ratio of 100:1. If a trader's account falls below the minimum amount required to maintain an open position, he will receive a "margin call" requiring him to either add more money into his or her account or to close the open position. Most brokers will automatically close a trade when the margin balance falls below the amount required to keep it open. The amount required to maintain an open position is dependent on the broker and could be 50% of the original margin required to open the trade.