Spot Rate, S 

Spot exchange rate 
Domestic Annual Interest Rate (%) 

Use annual interest rate in home country, such as 5(%); id = annual rate * (Days of Forward Contract / 360) 
Foreign Annual Interest Rate (%) 

Use annua interest rate in foreign country, such as 5(%);if = annual rate * (Days of Forward Contract / 360) 
Days till Maturity of the Forward Contract 

Could be 90 days, 180 days, 270 days, or 360 days, etc. Use a 360day year to calculate the partial interest rate. For example, 90 days is 1/4 of a year 
Forward Rate, F 

Forward exchange rate based on Interest Rate Parity 
Forward Premium / Discount 

Forward premium or discount 