Butterfly spread calculator

Calculate a long or short call or put butterfly at expiration, including entry debit or credit, profit, maximum risk, two break-even prices and a payoff table.

Strategy

Uses one lower-strike option, two middle-strike options and one upper-strike option.

Option type

With equal wings, calls and puts have the same expiration payoff shape.

Currency

Formatting only; no exchange-rate conversion.

Stock price at expiration

Use 0 to test the full downside boundary.

Lower strike

Lower-strike premium per share

Middle strike

Middle-strike premium per share

This leg uses two option contracts.

Upper strike

Upper-strike premium per share

Number of butterflies

Each butterfly contains four option contracts: 1 + 2 + 1.

Shares per option contract

US equity options commonly use 100; verify your contract.

Total fees

Enter all opening and expiration fees for the four legs.

Profit / loss at expiration—

Net debit—

Lower break-even—

Upper break-even—

Maximum profit—

Maximum loss—

Return on maximum risk—

Wing width—

Result outside both wings—

Stock price at expiration	Butterfly intrinsic value	Net profit / loss

How a butterfly spread works

A standard butterfly uses three equally spaced strikes and four option contracts. A long call butterfly buys one lower call, sells two middle calls and buys one upper call. A long put butterfly buys the lower and upper puts and sells two middle puts. At expiration, equal-wing call and put butterflies have the same triangular payoff.

A short or reverse butterfly takes the opposite positions: it sells the outside strikes and buys two middle-strike options. It benefits when the stock finishes outside the wings and has its largest loss at the middle strike. This page consolidates butterfly spread, call or put butterfly, long or short butterfly, profit, payoff and break-even calculations in one URL. An iron butterfly is a different four-leg structure and is not modeled here.

Butterfly spread formulas

Wing width = middle strike − lower strike = upper strike − middle strike

Long intrinsic value per share = max(0, wing width − |stock price − middle strike|)

Long profit = shares × (intrinsic value − gross debit) − fees

Short profit = shares × (gross credit − intrinsic value) − fees

Gross debit or credit per share equals lower premium plus upper premium minus two times the middle premium. Total shares equal the number of butterflies multiplied by shares per contract. Fees are allocated across those shares when calculating break-even prices.

Checked examples

Long butterfly: strikes US$95/US$100/US$105, premiums US$7.20/US$4.20/US$2.20, one butterfly of 100 shares and US$4 total fees produce a US$104 net debit and maximum loss. At stock price US$100, expiration profit and maximum profit are US$396. Break-even prices are US$96.04 and US$103.96.

Short butterfly: with the same strikes, premiums, quantity and fees, the net credit and maximum profit are US$96. At stock price US$100, the maximum loss is US$404. Break-even prices are US$95.96 and US$104.04.

How to interpret the results

Net debit or credit includes total fees. Long butterflies pay a debit; short butterflies receive a credit.
Maximum profit and loss occur only at expiration under the assumptions below. A long butterfly peaks at the middle strike; a short butterfly has its maximum loss there.
Break-even prices are expiration prices where net profit is zero after fees.
Return on maximum risk divides maximum profit by maximum loss. It is not an annualized return or probability.

Assumptions and limits

The three strikes must be strictly increasing and equally spaced. Broken-wing butterflies are not modeled.
The calculator models expiration payoff only. It excludes time value, implied-volatility changes, early exercise, assignment before expiration, dividends, taxes, bid-ask spreads and margin requirements.
All four contracts use the same expiration and multiplier. Premiums are entered per share.
Inputs are user-supplied, not live quotes. Results are educational estimates, not investment advice.

Quote check: a net debit or credit equal to or wider than the wing width would imply no positive risk at one boundary. The calculator rejects that input so stale, inverted or inconsistent quotes are not presented as a valid standard butterfly.

Related calculators

Use the Options Profit Calculator for a single call or put; the Option Credit Spread Calculator for vertical spreads; the Iron Condor Calculator for a four-strike range strategy; and the Straddle Calculator for a same-strike call and put.