Iím struggling to understand how margin and trade size works in Forex ?, futures you have set contract size and a margin requirement for that contract, for example the Spi has a margin of $2750 per contract and a point value of $25 all of which are set although margin does fluctuate at times, so a 10 point move equals $250, with forex am I right in thinking you CHOOSE YOUR TRADE SIZE and margin is a percentage of that trade size ?, e.g. I trade $50,000 worth of AUD/USD then my margin requirement with for example IB is 2.5% so is $1250 and each big point move is $500, so a tick is 1/100 so $5 ?.
I see some providers seem to quote a figure of 1 which equals $100,000 and 0.5 which equals $50,000, 0.25 equals $25,000 etc so is there set trade size or is it user defined or does it vary provider to provider as I also see there is mini forex and even micro forex
Just as an example I could choose to risk 2% or $200 of a $10,000 account and if I determine my risk to be 53 pips therefore my trade size would be buy/sell $37,700 AUD/USD as that would equal 1 pip to be $3.77, so x 53 would equal $199.81 and the margin required on that using IB, s 2.5% is $942.50?.
One last question in regard to margin, does this change as a position moves, e.g. increases when the position is in a loss or decreases when in profit?