FX Option Vertical Spread Calculator

How the FX option vertical spread is calculated

A vertical spread combines two calls or two puts on the same underlying orientation and expiry but at different strikes. The calculator labels the lower strike and higher strike explicitly, so the leg direction follows from the chosen construction. A bull call is long the lower-strike call and short the higher-strike call. A bear call reverses those call legs. A bear put is long the higher-strike put and short the lower-strike put, while a bull put reverses those put legs.

Every rate on this page uses quote currency per one base-currency unit. For EUR/USD, a strike of 1.10000 means USD 1.10 per EUR 1. Premiums use the same per-base-unit convention. Entering 0.02500 with a EUR 100,000 notional therefore represents USD 2,500 before costs. The calculator does not assume a 100,000-unit lot, exchange multiplier or broker contract size; the direct notional you enter is the only scale factor.

At expiry, a call contributes the greater of spot minus strike or zero. A put contributes the greater of strike minus spot or zero. The long leg receives that intrinsic value and the short leg contributes the opposite sign. Because both options share the same type and notional, their slopes offset outside the strike interval. That is why the four supported verticals have defined payoff bounds in this expiry-only arithmetic.

Premium outlay is signed. A positive value is a net debit and a negative value is a net credit. The tool accepts the premiums exactly as entered instead of assuming that a named debit or credit construction has a particular market quote. An unusual sign can result from stale, mismatched or mistyped premiums, so it should prompt an input review rather than a conclusion about the market.

The entered transaction cost is one non-negative quote-currency amount for the complete modeled position. It reduces every displayed outcome and is included in the numerical break-even. It is not allocated across legs, converted from pips or estimated from a broker schedule. Commission, spread, slippage, financing, tax, exercise fees and operational charges must be aggregated by the user if they belong in the scenario.

The three-point audit evaluates net P&L at spot zero, the lower strike and the higher strike. A plain vertical payoff is linear between strikes and constant outside them, so those points contain its minimum and maximum. The calculator linearly locates a non-negative break-even root when the endpoint signs cross. A missing root can arise when entered premium and cost make the modeled position profitable or unprofitable across the whole non-negative spot domain.

This route is for expiry planning, not mark-to-market analysis. Before expiry, each leg retains time value and responds to volatility, rates and the changing spot level. Use the separate price-scenario calculator for a model repricing before expiry and the portfolio-Greeks calculator for local sensitivity aggregation. Neither substitutes for a synchronized executable quote from the relevant venue or dealer.

Worked example from the audited fixture

How to interpret the result

1. Verify that both options share the same currency orientation, expiry, exercise style, settlement terms and base notional before treating the legs as one vertical.
2. Read a positive net P&L only as the result of the entered expiry spot. It does not state the likelihood of reaching that spot or the path taken before expiry.
3. Compare the net premium sign with the selected construction. An unexpected debit or credit is a reason to recheck leg premiums and bid-versus-ask sides.
4. Use the maximum gain and loss as expiry-payoff bounds after the one entered cost, not as broker margin, account risk or guaranteed execution outcomes.
5. Use the payoff audit to see where the cap arises: the higher-strike leg offsets further call movement, while the lower-strike leg offsets further put movement.
6. Recalculate with plausible expiry spots and realistic all-in costs. A single favorable scenario should not be treated as a strategy recommendation.

Assumptions and limitations

• No live spot, option chain, bid, ask, volatility surface, yield curve, account, position, order, execution, exercise, assignment or settlement feed is connected.
• Only equal-notional, same-expiry plain-vanilla call or put verticals are supported. Ratios, calendars, diagonals, barriers, digitals and path-dependent options are excluded.
• The calculation is at expiry. Time value, implied volatility, interest rates, skew, early closeout and mark-to-market P&L are not calculated.
• The entered total cost is user supplied. The page does not estimate spread, slippage, commission, financing, collateral, tax or exercise fees.
• Short-option assignment and exercise mechanics, deliverability, cash settlement, cut times, holidays, counterparty terms and pin risk are not modeled.
• Maximum loss is not a margin requirement or account liquidation threshold. Provider rules and jurisdictional protections can materially change operational risk.
• No strike, premium, expiry, option leg, spread construction, provider, broker, hedge, signal or trade is recommended.

Sources and methodology

The arithmetic is independently fixture-tested. These primary market and industry-education references support the visible construction and payoff terminology; they do not verify an entered quote, exposure, contract, provider or market timestamp.

• Options Industry Council — Bull Call Spread — Primary industry-education reference for the two-call construction and defined expiry trade-off.
• Options Industry Council — Bear Put Spread — Primary industry-education reference for the two-put bearish construction.
• Options Industry Council — Options Strategies Quick Guide — Primary strategy guide for leg construction, break-even and limited-risk terminology.