current spot rate is the strike price is the cumulative normal distribution function is domestic risk free simple interest rate is foreign risk free simple interest rate is the time to maturity (calculated according to the appropriate day count convention) and is the volatility of the FX rate. Risk management An earlier pricing model was published by Biger and Hull, Financial Management, spring 1983. The model preceded Garman and Kolhagen Model. A wide range of techniques are in use for calculating the options risk exposure, or Greeks (as for example the Vanna-Volga method). Although the option prices produced by every model agree (with Garman–Kohlhagen), risk numbers can vary significantly depending on the assumptions used for the properties of spot price movements, volatility surface and interest rate curves. After Garman–Kohlhagen, the most common models are SABR and local volatility, although when agreeing risk numbers with a counterparty (e.g. for exchanging delta, or calculating the strike on a 25 delta option) Garman–Kohlhagen is always used. References Options (finance) Derivatives (finance)