To calculate a forward FX rate, use the formula; Forward rate = Spot rate*(1 + r1)^n
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(1 + r2)^n where r1 is the relevent interest rate for currency 1,
r2 is the relevent interest rate for currency 2,
n is the period in question In terms of the interest rate to be used, it should be the risk free rate for the period in wuestion for each currency.