Butterfly Spread¶
OVERVIEW¶
A butterfly spread is a neutral options strategy built from four contracts across three equidistant strikes, designed to profit when the underlying closes at or near the middle strike on expiration day. The payoff diagram resembles a tent or the wings of a butterfly, hence the name. Both risk and reward are strictly capped. Butterflies are the cheapest way to express a specific price-target view — the trader is paid to be precisely right about where the stock will trade on a specific date, which is why they are a favorite of high-conviction event traders and low-volatility harvesters.
CONSTRUCTION¶
The standard long call butterfly uses four contracts at three strikes where K1 < K2 < K3 and the strikes are equidistant (K2 − K1 = K3 − K2):
| Leg | Position | Strike | Moneyness |
|---|---|---|---|
| 1 | Long 1 call | K1 | In-the-money |
| 2 | Short 2 calls | K2 | At-the-money |
| 3 | Long 1 call | K3 | Out-of-the-money |
All contracts share the same expiration date. The position can also be built with puts (long put butterfly), producing an identical P&L profile. Iron butterflies substitute puts on the downside leg and calls on the upside leg, creating a short straddle + long strangle combination that opens for a net credit rather than a debit.
Key Formulas¶
| Value | Formula |
|---|---|
| Net debit | Premium(K1) − 2 × Premium(K2) + Premium(K3) |
| Max profit | (K2 − K1) − Net debit, at expiration with underlying at K2 |
| Max loss | Net debit, if underlying closes ≤ K1 or ≥ K3 |
| Lower breakeven | K1 + Net debit |
| Upper breakeven | K3 − Net debit |
WORKED EXAMPLE¶
Setup: SPY trades at $500.00 on 2026-04-21. A trader expects SPY to pin near $500 into the 2026-05-16 monthly expiration and opens a 490/500/510 call butterfly.
| Leg | Contract | Premium |
|---|---|---|
| Long 1 call | May 16 $490 call | $12.00 debit |
| Short 2 calls | May 16 $500 calls | $5.00 credit each = $10.00 credit |
| Long 1 call | May 16 $510 call | $1.00 debit |
Results:
| Metric | Value |
|---|---|
| Net debit | $12.00 − $10.00 + $1.00 = $3.00/share ($300/spread) |
| Max profit (SPY = $500 at expiry) | $10 wing width − $3 debit = $7.00 × 100 = $700 |
| Max loss | $300 (SPY finishes below $490 or above $510) |
| Lower breakeven | $493 |
| Upper breakeven | $507 |
| Return on risk | $700 / $300 = 233% |
The trader risks $300 to make up to $700 over 25 days — a payoff profile that pays only if SPY closes within a $14 window.
WHEN TO USE¶
Butterflies are the go-to structure for earnings pins, FOMC day pins, and index max-pain expirations. A trader with a strong view that NVDA will close near $140 on earnings — without wanting to pay the full cost of a long straddle — can buy a 135/140/145 butterfly for a fraction of the straddle premium. Portfolio hedgers use broken-wing butterflies (unequal wings) to skew payoff toward downside tail protection without paying the upfront premium of a long put. Iron butterflies are a standard income trade for traders who want defined risk on short-volatility views, replacing undefined-risk short straddles.
LIMITATIONS¶
Butterflies are highly sensitive to exact strike selection — missing the center strike by one increment dramatically reduces the payoff. They are also sensitive to implied volatility: buying a butterfly into an earnings event with inflated IV means paying a higher debit for the same wing width, cutting the maximum return. Commissions matter too: four legs per butterfly, eight on an iron fly, so contract-cost drag is material on small-size accounts. Finally, max profit is only achieved at expiration and only at the exact middle strike — closing early rarely captures more than 60–70% of theoretical max, because extrinsic value remains on the short strikes until the final session.