FX Option
Also known as: Currency option, Vanilla FX option
The right to exchange currencies at a set rate — hedging with the upside left open.
1 · SnapshotThe one idea to remember
2 · BeginnerWhat is it, really?
An FX option gives the right — not the obligation — to exchange one currency for another at a fixed rate before or at a set date. Every FX option is two-faced by nature: a call on euros is a put on dollars; buying the right to sell dollars cheap is the same as buying the right to buy euros cheap.
The classic user is a company bidding on a foreign contract: it might win $50M of revenue in three months — or might not. A forward would lock a hedge on money it may never receive; an option hedges the maybe: pay a premium now, exercise only if the bid wins and the rate moved against them.
Macro traders love FX options for a different reason: they're the cleanest way to bet on turbulence or calm in a currency, not just direction.
- Asset class
- FX derivatives
- Instrument type
- Option (call/put on a pair)
- Traded
- OTC (deep interbank market)
- Typical users
- Corporates, macro funds, dealers
3 · IntermediateHow it works in practice
How the FX options market talks
The interbank market quotes not prices but implied volatilities, and organises them in a peculiar, elegant grid per tenor:
- ATM vol: the at-the-money volatility level.
- Risk reversal (RR): vol of 25-delta call minus 25-delta put — the smile's tilt. A EUR/USD RR "for dollar calls" says crashes are feared in one direction.
- Butterfly (BF): how much the wings sit above ATM — the smile's curvature, i.e. the price of tail events.
Three numbers per tenor reconstruct the whole smile — a convention unique to FX.
Delta conventions
Strikes are referenced by delta (25d, 10d), not currency levels — and whether delta is spot/forward, premium-adjusted or not, differs by pair. Real desks live and die by getting the convention right.
Structures corporates actually buy
- Collars/risk reversals: buy protection, sell away some upside — cheap or zero-cost.
- Participating forwards: full protection, keep half the upside.
- Straddles/strangles: the volatility trades around elections and central-bank meetings.
4 · AdvancedPricing & valuation
Garman–Kohlhagen
Black–Scholes with the foreign interest rate as a "dividend yield" — a call on the base currency:
What the symbols mean
- Cthe price of a call option
- Sthe price of the underlying today
- rthe interest rate, per year
- Tmaturity, in years
- Nthe normal distribution, or a count
- Kthe strike: the price written into the contract
Domestic-foreign symmetry: a EURUSD call priced in USD equals the corresponding USD put priced in EUR, converted — a consistency check that catches convention bugs.
Smile construction and models
From ATM/RR/BF quotes per tenor, desks build the smile (SVI/vanna-volga/parametric), then a full surface. For exotics, calibrated dynamics matter: local vol underprices barrier/one-touch structures, stochastic vol (Heston) overshoots elsewhere — local-stochastic vol (LSV) mixtures tuned to vanillas and one-touch quotes are the FX-desk standard, because the market for touch products is liquid enough to discipline the model.
Vanna and volga
FX desks manage second-order smile Greeks explicitly: vanna (∂delta/∂vol) and volga (∂vega/∂vol) — the vanna-volga method prices simple exotics off the cost of hedging exactly these with RR and BF instruments.
What the surface reveals
Risk reversals are among macro's best sentiment gauges: EM pairs show persistent skew toward devaluation; pegged pairs price regime break as a far-wing hump. Breeden–Litzenberger on the smile yields full risk-neutral densities — event probabilities readable before referendums and elections.
The formulas above are standard textbook formulations, simplified for teaching. They explain the mechanism — they are not a valuation tool, and they will not reproduce a dealer’s price.