The following form will help you to determine the best size of your position. The system adjusts the size for the pair you trade, your equity, the entry and exit prices and, of course, the maximum risk per trade.
Depending on your account (equity, currency of the account) the pair you trade and the risk you accept on one trade, the programme will calculate the exact position sizing you have to use for your trade. Many brokers don't allow the possibility of trading with variable contract sizes so that's the reason why we've added the number of contracts you have to trade in the table. The risk and leverage are updated for each case.