How Lot Sizes and Free Margin Control Your Forex Account

When beginners look into Forex trading, the first question is usually about cost. You might wonder what the minimum deposit is and how much it actually costs to open a position.

Many new traders deposit funds—say, $200—expecting they can trade freely. But they soon find that after opening just one trade, minor market movements wipe out their account. This happens because they do not understand how trading sizes and account margin work together.

Understanding the mechanical side of your trading account stops you from taking on risks you cannot afford.

Understanding Your Trade Size

In Forex, you do not buy individual dollars or euros. You trade in bundles called lots. The international standard is one Standard Lot, which equals 100,000 units of the base currency. Because this is too large for most retail accounts, brokers offer smaller sizes:

• A Mini Lot (0.1) equals 10,000 units.
• A Micro Lot (0.01) equals 1,000 units.

If you are trading a currency pair where the US Dollar is the base (like USD/JPY) and you open 0.1 lots, your trade has a total notional value of $10,000.

Used Margin Acts as a Security Deposit

You do not need $10,000 in cash to open that 0.1 lot trade. Instead, brokers provide leverage. If your broker offers 100:1 leverage, you only need to put up 1% of the total value to control the position.

For a $10,000 trade, that means your broker requires $100 from your account to hold the position open. This $100 is called your Used Margin. It is locked up until you close the trade.

This mechanism applies whether you are trading spot currency pairs or using Contracts for Difference (CFDs), which allow you to speculate on price movements without owning the underlying asset. Leverage lets you control large positions, but it also ties up your margin.

Free Margin is Your Survival Money

The money sitting in your account that is not tied up in Used Margin is your Free Margin. This is the most critical number on your trading screen.

Free Margin serves two purposes. First, it provides the funds available to open new positions. Second, it acts as your shock absorber if an existing trade moves against you.

You can calculate it with a simple formula:

Free Margin = Equity - Used Margin

Your Equity is your total account balance plus any floating profits (or minus any floating losses) from your open trades.

Imagine you deposit $200 and open that 0.1 lot trade requiring $100 in Used Margin. If the price has not moved, your Equity is still $200.

Free Margin = $200 (Equity) - $100 (Used Margin) = $100.

You have exactly $100 of breathing room. If the market drops and you are sitting on a $50 floating loss, your Equity drops to $150. Your Free Margin shrinks to $50. If the market continues falling until your floating loss hits $100, your Free Margin hits zero. At this point, the broker will start force-closing your trades—an event known as a Margin Call or Stop Out—to prevent your account from going into a negative balance.

Give Your Account Room to Breathe

The most common reason small accounts disappear is not bad strategy, but bad sizing. If you open a 0.1 lot trade on a $200 account, your $100 of Free Margin can only withstand about 100 pips of price movement before your money is gone.

To survive when the market gets volatile, you must trade at a size that matches your capital. Trading 0.01 lots instead of 0.1 lots lowers your Used Margin, drastically increasing your Free Margin and giving your trade the space it needs to weather normal price swings. Alongside managing your margin, surviving the market also means trading in a secure environment. Before depositing your capital, it is good practice to run your chosen brokers name through the WikiFX app to verify their regulatory status and ensure your funds are being handled by a legitimate platform.