Iron Butterfly - A Short Straddle With the Tails Cut Off

By EC Assets Research Team, Derivatives Strategy · Published 13 August 2026 · Updated 13 August 2026

Iron Butterfly: An iron butterfly sells an at-the-money call and put and buys a further out-of-the-money call and put as wings, collecting a net credit. It is a short straddle with the unlimited tails removed: maximum profit if the underlying pins the centre strike, maximum loss capped at the wing width minus the credit.

The Structure

An iron butterfly combines four options at three strikes, all in the same expiry: sell one at-the-money call and one at-the-money put at the centre strike, buy one out-of-the-money put below and one out-of-the-money call above as wings. The position is opened for a net credit, and the wings are usually placed symmetrically.

Read as components, it is a short straddle wrapped in protection. Read as spreads, it is a bull put spread and a bear call spread sharing their short strike. Both readings are exact, and the second explains the margin treatment: risk is defined on each side by the distance to the wing.

The Arithmetic

Maximum profit = net credit, earned if the underlying settles exactly at the centre strike Maximum loss = wing width - net credit Breakevens = centre strike ± net credit

With the underlying at 100, selling the 100 straddle for 7.20 and buying the 90 put and 110 call for a combined 1.70 nets 5.50. The position earns something between 90 plus and 110 minus a bit, earns its full 5.50 only at exactly 100, and cannot lose more than 10.00 - 5.50 = 4.50 on either side.

Butterfly or Condor

The iron condor sells an out-of-the-money strangle instead of the straddle, creating a plateau of maximum profit between its two short strikes. The butterfly concentrates everything on one point: a larger credit, because at-the-money options carry the most time value, in exchange for a profit zone that is a single price rather than a range.

The practical consequence is that a condor wins often and modestly, while a butterfly wins rarely at its maximum but collects so much premium that it tolerates a miss. The breakevens tell the story: in the example above the position is profitable anywhere between 94.50 and 105.50, a wider corridor than the credit of a comparable condor would buy. The choice between them is a view on the shape of the expected distribution, not merely on its width: the butterfly is the sharper bet that the underlying finishes near where it already trades.

The Greeks of the Position

At inception the position is close to delta-neutral, short gamma and long theta, the standard signature of sold premium. Two features are worth singling out.

Theta is front-loaded at the centre. The short at-the-money options decay faster than the wing protection, and that decay accelerates into expiry, which is why the structure is popular in the final weeks of an expiry cycle.

Gamma risk concentrates at the strikes. Near the centre strike close to expiry, delta flips violently with small moves, and the maximum-profit point sits exactly where the position is hardest to manage. Pinning the centre is the best outcome and the most nerve-racking path to it.

Vega is short. A rise in implied volatility hurts the position even if the underlying does not move; a volatility collapse, for instance after an event, helps it. Butterflies opened just before scheduled announcements are effectively selling the event premium, with the wings capping what a surprise can cost.

Worked Example

A stock trades at 100 ahead of a quiet month. A trader sells the 100 call and 100 put for 7.20 total and buys the 90 put and 110 call for 1.70, netting 5.50 on a 10-point wing.

At expiry with the stock at 101, the short call is worth 1.00 and everything else expires worthless: profit 4.50. At 100.10, profit is 5.40, nearly the maximum. At 88, the put side is fully in the money and capped by the wing: loss 4.50, the defined maximum, regardless of whether the stock is at 88 or 60. The wing converts a catastrophic outcome into a budgeted one, and the cost of that conversion was the 1.70 paid for protection that usually expires worthless.

[!key] An iron butterfly is a short straddle with bought wings: maximum profit equals the credit and requires a finish at the centre strike, maximum loss is the wing width minus the credit, and the breakevens sit a full credit away from the centre on each side.

[!warning] The structure is short gamma where it matters most: at the centre strike into expiry, small moves swing the outcome sharply, and the maximum-profit scenario is also the highest-stress path. Positions held to the final days should be sized for that regime, and the credit should never be mistaken for the expected profit; the expected outcome is far below the maximum.

Why It Matters for Institutional Investors

• Defined-risk premium selling. The butterfly expresses the same view as a short straddle while remaining sizeable against a hard risk limit, which is what makes sold volatility usable inside mandated portfolios.
• Event pricing in one trade. Around scheduled announcements the structure isolates the question of whether the implied move is overpriced, with a known worst case if it is not.
• A shape view, not a size view. Choosing a butterfly over a condor is a statement about where the distribution's mass sits, which is a more refined expression than simply being short volatility.

References

1. McMillan, L. G. (2012). Options as a Strategic Investment (5th ed.). Prentice Hall.
2. Natenberg, S. (2015). Option Volatility and Pricing (2nd ed.). McGraw-Hill.
3. Sinclair, E. (2020). Positional Option Trading. Wiley.
4. Bennett, C. (2014). Trading Volatility, Correlation, Term Structure and Skew.
5. Hull, J. C. (2022). Options, Futures, and Other Derivatives (11th ed.). Pearson.