Iron Butterfly Explained
An iron butterfly sells an at-the-money call and put and buys wings around them: a defined-risk trade that collects a large credit and profits if the underlying pins the strike.
What it is
An iron butterfly sells an at-the-money call and an at-the-money put, the short straddle, and buys a further out-of-the-money call and put as protective wings. You collect a large net credit because the at-the-money options are expensive, and you keep the most if the underlying finishes exactly at the short strike. The bought wings cap the loss on either side, making it a defined-risk version of a short straddle. It is a sharp, high-credit range trade: the profit zone is narrow and centred on the strike, but the maximum loss is known and limited.
Payoff at expiration
When to use it
Use an iron butterfly when you expect the underlying to sit very close to a specific level into expiration and implied volatility is high, so the at-the-money credit is rich. It is a tighter, higher-credit cousin of the iron condor: choose it over a condor when you have a strong pin thesis and want maximum premium, and the condor when you want a wider, more forgiving profit zone. Centre the short strike where you expect the underlying to land, choose about 30 to 45 days, and avoid events that can gap the underlying away from the strike, which is exactly where this structure hurts most.
Greeks profile
| Delta | Near zero at entry when centred at-the-money, since the short call and put deltas offset. |
| Gamma | Short gamma, and sharply so near the strike, so losses build quickly as the underlying moves away from the centre. |
| Theta | Positive and large. The at-the-money short options decay fast in your favour, which is the engine of the trade. |
| Vega | Short vega. A drop in implied volatility helps strongly; a spike hurts because the short at-the-money options gain value. |
Max profit, max loss & break-evens
Max profit = net credit received, reached only if the underlying finishes exactly at the short strike. Max loss = wing width − net credit, realised beyond either long strike. Lower BE = short strike − net credit · Upper BE = short strike + net credit
Concrete example
A stock trades at 100. You sell the 100 call and the 100 put, collecting 8 together, and buy the 90 put and the 110 call for 1.50 total, a net credit of 6.50. Max profit is that 6.50 if the stock pins 100 at expiration. Break-evens are 93.50 and 106.50. Max loss is the 10-point wing width minus the 6.50 credit, so 3.50, if the stock closes below 90 or above 110. You collect a rich credit for a narrow bet that the stock stays near 100.
Risks & management
The profit zone is narrow, so the underlying only has to drift a few points from the strike to erase the credit, and the short gamma means losses build quickly once it does. The wings cap the maximum loss, which is the structure's safety net, but that loss is realised on any decisive move. Manage before expiry: take profit when the underlying sits near the strike and much of the credit is captured, roll the untested side or the whole structure if price drifts, and never hold through an event that can gap the underlying out of the narrow zone. Assignment risk lives on the short options near expiry if they finish in-the-money.
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