How do I calculate profits and losses?

When you close out a trade, you can calculate your profits and
losses using the following formula:
Price (exchange rate) when selling the base currency – price
when buying the base currency X transaction size = profit
or loss
Assume you buy Euros (EUR/USD) at 1.2178 and sell Euros at
1.2188. If the transaction size is 100,000 Euros, you will have a
$100 profit.
($1.2188 – $1.2178) X 100,000 = $.001 X 100,000 = $100
Similarly, if you sell Euros (EUR/USD) at 1.2170 and buy Euros
at 1.2180, you will have a $100 loss.
($1.2170 – $1.2180) X 100,000 = – $.001 X 100,000 = – $100
You can also calculate your unrealized profits and losses on open
positions. Just substitute the current bid or ask rate for the action
you will take when closing out the position. For example, if you
bought Euros at 1.2178 and the current bid rate is 1.2173, you
have an unrealized loss of $50.
($1.2173 – $1.2178) X 100,000 = – $.0005 X 100,000 = – $50
Similarly, if you sold Euros at 1.2170 and the current ask rate is
1.2165, you have an unrealized profit of $50.
($1.2170 – $1.2165) X 100,000 = $.0005 X 100,000 = $50

If the quote currency is not in US dollars, you will have to con-
vert the profit or loss to US dollars at the dealer’s rate. Further, if
the dealer charges commissions or other fees, you must subtract
those commissions and fees from your profits and add them to
your losses to determine your true profits and losses.
How much money do I need to trade forex?
Forex dealers can set their own minimum account sizes, so you will
have to ask the dealer how much money you must put up to begin
trading. Most dealers will also require you to have a certain amount
of money in your account for each transaction. This security
deposit, sometimes called margin, is a percentage of the transaction
value and may be different for different currencies. A security
deposit acts as a performance bond and is not a down payment or
partial payment for the transaction.
Dealers who are regulated by NFA are required to calculate and
collect security deposits that equal or exceed the percentage set by
NFA rules. Although the percentage of the security deposit remains
constant, the dollar amount of the security deposit will change
with changes in the value of the currency being traded