Iron Butterfly
An iron butterfly is a four-legged options strategy that combined a short straddle at-the-money with a long strangle one or two strikes further out, creating a defined-risk, limited-profit structure that profited when the underlying asset remained close to the central strike at expiry.
The iron butterfly brought together four option legs: sell an ATM call, sell an ATM put, buy an OTM call at a higher strike, and buy an OTM put at a lower strike — all on the same underlying and same expiry. The resulting payoff was a tent-shaped profit zone centred on the short strikes, with maximum profit earned when the underlying closed exactly at the short strike on expiry day, and losses capped at the width of either wing minus the net premium collected.
In Indian markets, Nifty 50 and Bank Nifty weekly options were the primary vehicles for iron butterfly deployment. Traders who expected the index to remain range-bound after a period of elevated implied volatility — perhaps following an RBI policy announcement or a Union Budget — found the structure attractive. Because NSE's weekly contracts expired every Thursday for Bank Nifty (until the SEBI circular rationalising weekly expiries in late 2023) and Friday for Nifty, the iron butterfly was particularly suited to short-duration, high-theta decay plays.
The risk-reward profile of an iron butterfly differed from the iron condor in one key respect: the short strikes were identical rather than separated. This produced a higher net credit collected (because both ATM options had more premium) but a narrower profit zone. A Nifty iron butterfly centred at 22,000 with wings at 21,700 and 22,300 collected more premium than an iron condor with short strikes at 21,900 and 22,100, but the tent of profitability was much narrower — Nifty had to close very close to 22,000 to realise the full profit.
Management of the trade involved monitoring delta and gamma closely. Since the short options were at-the-money, gamma was at its highest, meaning the position's delta could shift rapidly as the underlying moved even modestly. Many traders adjusted by closing the threatened wing and rolling it closer to the current underlying price when the index moved significantly, effectively converting the structure into a new butterfly centred at the new level.
Implied volatility played a critical role. If IV expanded after entry — for example, if a surprise macroeconomic data point caused panic buying of options — the short ATM options gained value and the position moved against the seller. Conversely, IV crush following a widely anticipated event was the scenario that accelerated realised profit. SPAN margin requirements for the iron butterfly were lower than for naked straddles because the long wings provided capital protection, making the structure accessible to participants with moderate F&O margin balances.