Butterfly Spread
A butterfly spread is a neutral options strategy combining three strikes — a long position at the lowest and highest strikes and two short positions at the middle strike — to profit from minimal price movement in the underlying near expiry, with both maximum loss and maximum profit capped.
The butterfly spread was constructed using three equidistant strikes, typically all calls or all puts. The classic long call butterfly involved purchasing one lower-strike call, writing two middle-strike calls, and purchasing one higher-strike call. The strategy produced a tent-shaped payoff diagram, with the peak profit occurring precisely at the middle strike at expiry and losses limited to the net debit paid anywhere outside the outer strikes.
In NSE's liquid index options environment, butterfly spreads found use around scheduled events such as the Union Budget, RBI policy meetings, or quarterly index rebalancing, when traders expected the index to remain within a specific range. For example, with Nifty at 22,000, a trader might execute a butterfly by purchasing a 21,500 call, writing two 22,000 calls, and purchasing a 22,500 call. The net debit was typically a fraction of the total spread width, making the risk-reward ratio appear attractive — though achieving the maximum profit required Nifty to land almost exactly at 22,000 at expiry.
The iron butterfly was a related variant that combined a written straddle at the middle strike with a purchased strangle at the outer strikes, resulting in a net credit position rather than a debit. The iron butterfly was functionally equivalent to the regular butterfly in terms of payoff profile but was structured differently for margin treatment. On NSE, the SPAN system applied spread margins to recognised butterfly structures, reducing the total margin compared to holding the legs independently.
Theta worked powerfully in favour of a butterfly spread as expiry approached, because the two written middle-strike options decayed faster than the long outer options. However, if the underlying made a sharp move early in the trade, the position could show significant losses that required active management. Vega was generally negative for a long butterfly — a rise in implied volatility harmed the position because it increased the value of the written options more than the purchased ones.
A common misconception was that the butterfly's capped risk made it a simple strategy. In practice, executing all three legs simultaneously at favourable prices required access to limit orders across multiple strikes, and the bid-ask spread across three contracts could substantially erode the theoretical edge. Traders on NSE typically used combination order facilities offered by brokers or executed legs in a specific sequence during liquid market hours to minimise slippage.