Butterfly spread: a cheap, defined-risk bet on a pin

A butterfly spread uses three evenly spaced strikes to pay off only if a stock pins near the middle strike at expiration — cheap to enter, risk capped at what you paid, and low-probability by design. This guide draws the payoff tent, runs the max-profit and break-even math, and walks a full worked example dollar by dollar. Research and education only — not financial advice.

A butterfly spread is a three-strike options position that pays off only if the stock pins near the middle strike at expiration: cheap to enter, loss capped at what you paid, and — because the payoff peak is razor-thin — low-probability by design.

What a butterfly spread actually is

The classic long call butterfly buys one call at a lower strike, sells two at a middle strike, and buys one at a higher strike — same stock, same expiration, strikes evenly spaced. The two calls you sell (the "body") finance most of the two you buy (the "wings"), so the net cost is small. That net debit is the whole price of the position, and the most you can lose.

The payoff diagram is a tent: flat and negative in both tails — below the lower wing and above the upper you lose the debit — rising to a sharp peak over the middle strike. You are betting on a pin: the stock sitting close to that center strike at expiration, and nowhere else.

Call, put, and iron variants

Several flavors draw the same tent: a long put butterfly (buy 1 high put, sell 2 middle, buy 1 low) is the identical payoff, and an iron butterfly sells an at-the-money straddle and buys wider wings for a credit — same shape, same pin thesis. A broken-wing butterfly uses unequal wings to skew the risk to one side.

The numbers that define every butterfly

A symmetric long butterfly reduces to a few one-line formulas, where the wing width is the distance from the body strike to either outer strike:

• Net debit = long wing premiums − the two short body premiums. This is what you pay, and your maximum loss.
• Max profit = wing width − net debit, earned only at the body strike at expiration.
• Lower break-even = lower strike + net debit.
• Upper break-even = upper strike − net debit.

The tell is the ratio. A cheap debit against a wing-width payoff makes the reward-to-risk look spectacular — often 3:1 or better — but that is the market pricing a low probability, not a gift. See risk-reward ratio: a fat ratio and a low win rate are the same coin.

A worked example, dollar by dollar

Suppose — a hypothetical teaching example, not a trade — stock XYZ trades at $100 and you expect it to sit near there in a month. You build a $95 / $100 / $105 call butterfly:

• Buy one $95 call for $6.00.
• Sell two $100 calls for $3.00 each ($6.00 collected).
• Buy one $105 call for $1.20.

One contract covers 100 shares, so every premium is × 100 in real dollars. Run the numbers:

• Net debit = $6.00 − $6.00 + $1.20 = $1.20 → $120 per butterfly (max loss)
• Wing width = $5.00
• Max profit = $5.00 − $1.20 = $3.80 → $380 per butterfly
• Break-evens = $96.20 and $103.80

Risk $120 to make $380 — a defined 1:3.2 — but only if XYZ pins the narrow band at expiration. Run it through every ending:

Green only between $96.20 and $103.80, the full $380 at one price, $100 — a free options profit calculator plots this tent for any three strikes before you commit.

Why the pin is so hard to hit

Three forces make a butterfly low-probability, and the seductive 1:3 ratio hides all of them.

The peak only exists at expiration

Before expiration the tent is rounded off. Even if the stock sits right on your body strike with a week to go, the two short calls still carry extrinsic value you would have to buy back, so the position is worth a fraction of its $380 peak — the sharp point only forms in the final day or two as that time value burns off via theta decay. A butterfly must be right on both price and timing: near the strike, and near expiration.

The profitable band is narrow

The green zone spans $96.20 to $103.80 — under 8% of the stock price. Most stocks travel that far in a week on ordinary noise, which is exactly why the payoff is priced so generously: the market knows the pin rarely holds.

The Greeks turn against a move

A long butterfly centered at the money is short gamma and short vega near expiration: a jump either way hurts fast, and a spike in implied volatility flattens the tent even if price has not moved. The flip side is the appeal — if the stock sits still and IV bleeds, both theta and the vol drop work for you. It is the textbook "nothing happens" trade.

When traders reach for it

Educationally, a butterfly fits a specific, nameable thesis rather than a direction. One is a pin into monthly expiration, where open interest at a round strike can act like a magnet into opex and a butterfly centered there expresses that view with defined risk. Another is a contained earnings move: placed at the expected post-report price, it profits if the move is muted and IV crushes — but a gap through a wing takes the full debit. See how to trade earnings for why the crush cuts both ways.

How the desk treats it

A butterfly still needs a level, timing, and an exit. Our desk never posts a bare "buy the fly on XYZ"; every idea ships as a card with a trigger, profit targets, a stop, and a time-stop, published to a public, timestamped paper/model record before the move — no real money, losers left on the board. Inspect it at the record, dead trades included, and see live cards under signals. Our published hypothetical backtest of the raw scanner, traded blind, logged a 46.6% simulated win rate and a 0.82 profit factor across 161 simulated trades — a gaudy reward-to-risk ratio means nothing until the win rate is set against it.

The 30-second recap

• A butterfly spread = buy 1 low, sell 2 middle, buy 1 high strike (evenly spaced); the net debit is the whole cost and max loss.
• Max profit = wing width − net debit, earned only at the middle strike at expiration. Break-evens = low strike + debit and high strike − debit.
• Worked example: pay $120, risk $120, cap the gain at $380, profit only between $96.20 and $103.80.
• It is low-probability by design: the peak exists only at expiration, the band is narrow, and four legs mean heavy transaction friction.

Common questions

Last updated 2026-07-11 · ClaudeQuantAlgo Research Desk · research and education only.

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