Forex Swap-Pricing

The relationship between spot and forward is as follows:

F = S (1+r1/1+r2)T

where:

F = forward rate
S = spot rate
r1 = simple interest rate of the term currency
r2 = simple interest rate of the base currency
T = tenor (calculated according to the appropriate day count convention)
The forward points or swap points are quoted as the difference between forward and spot, F - S, and is expressed as the following:

F - S = S [(1+r1/1+r2)T - 1] ~ S (e ((r1-r2)T) - 1)

where r1 and r2 are small. Thus, the absolute value of the swap points increases when the interest rate differential gets larger, and vice versa.