You can use this Margin Calculator to determine how much of your own money will be required by your broker for a trade.
In Forex a Lot is 100,000 units of currency. However, the margin defined on your account, by your broker is what determines how much of your own money you will be putting toward the trade.
For example, if you were to place a 1 Lot trade on USD/JPY and your margin was 200:1, you would be using $500 of your own money on the trade. Thus if you were only risking 2% of your account per trade you would need in excess of $25,000 USD in your account. Conversely, if you placed a micro-lot on a USD/JPY trade, you would only be using $5 of your own money. On a $100 account, that would be 5%.
- Standard Lot (1) = 100,000 units
- Mini-Lot (.1) = 10,000 units
- Micro-Log (.01) = 1,000 units.