This guide explains how a butterfly spread works on Nifty, the numbers on one lot, how to choose the width, how it behaves before expiry and how to manage, automate and test it.
At a glance
| Long call butterfly | |
|---|---|
| Market view | The index ends near a specific level at expiry |
| Legs | Buy 1 lower call, sell 2 middle calls, buy 1 higher call, same expiry, equal gaps |
| Cost | A small net debit |
| Maximum profit | The gap between strikes minus the debit, at the middle strike |
| Maximum loss | The debit |
| Breakevens | Lower strike plus the debit, and higher strike minus the debit |
| Time decay | Helps near the middle strike, mostly in the last days |
| Volatility | A fall in IV helps |
How a butterfly spread works
The two short calls at the middle strike earn the most when the index pins that strike. The two long calls on either side limit the risk in both directions. The trade is cheap because the middle calls pay for most of the outer ones.
A butterfly is a precise bet. It pays well in a narrow range and loses its small debit outside it. You can build the same shape with puts, or as an iron fly, which collects a credit instead of paying a debit.
The numbers on one lot
Using Black–Scholes model prices with Nifty at 25,000, 12 days to expiry, IV of 14% and a lot of 65:
- Buy the 24,800 call at ₹398.30
- Sell two 25,000 calls at ₹280.50 each
- Buy the 25,200 call at ₹187.50
- Net debit: ₹24.80 per unit, or ₹1,612 per lot
| Nifty at expiry | P&L per lot |
|---|---|
| 24,800 or lower | −₹1,612 |
| 24,825 | breakeven |
| 24,900 | +₹4,888 |
| 25,000 | +₹11,388 |
| 25,100 | +₹4,888 |
| 25,175 | breakeven |
| 25,200 or higher | −₹1,612 |
The best case pays about seven times the cost. In the model, the chance that Nifty finishes between the two breakevens is about 22%. A butterfly loses more often than it wins, and the wins are usually less than the maximum.
Interactive payoff chart: change the spot, IV, lot size and days to expiry to see the curve, breakevens and Greeks.
Choosing the width
| Wings | Debit per lot | Maximum profit per lot | Profit range at expiry | Chance of profit (model) |
|---|---|---|---|---|
| 100 points | ₹403 | ₹6,097 | 24,906 to 25,094 | about 12% |
| 200 points | ₹1,612 | ₹11,388 | 24,825 to 25,175 | about 22% |
| 300 points | ₹3,591 | ₹15,909 | 24,755 to 25,245 | about 30% |
Wider wings cost more and pay more, and the profit range is wider. Narrow wings are cheap lottery tickets on a pin.
The middle strike
Most traders centre the butterfly at the money, or at a level the index is likely to gravitate to, such as the strike with the highest open interest or the max pain level near expiry. A butterfly centred away from the money is a cheap directional trade: one centred at 25,200 profits only if Nifty rises to around that level.
How a butterfly behaves before expiry
At entry the 200-point butterfly has almost no delta, a theta of about +₹68 a day per lot and a vega of about −₹113 per lot for each 1-point rise in IV. Its value grows slowly at first and quickly at the end.
With Nifty unchanged at 25,000, the model shows a profit of about ₹657 per lot with 6 days left, ₹2,201 with 2 days left and about ₹7,164 in the final hours of expiry day. Most of the payoff arrives on the last day, so a butterfly opened a week out needs the index to stay near the middle strike for the whole week.
When a butterfly works, and when it does not
Works best when:
- You expect a quiet expiry close to a known level.
- IV is high and likely to fall.
- Expiry is a few days away, so the payoff can build.
Struggles when:
- The index trends away from the middle strike.
- A large move happens on expiry day, the day the butterfly needs calm.
- Bid-ask spreads are wide: four legs in and out can cost a large share of a small debit.
Managing a butterfly
- Take profits before the last minutes. Pinning the exact strike is rare. Many traders close at 30% to 50% of the maximum profit.
- Accept the debit as the stop. The loss is limited, so many traders let a losing butterfly expire rather than pay to exit.
- Shift if the view changes. Close and open a new butterfly centred at the new level.
Butterfly vs similar strategies
| Long call butterfly | Iron fly | Short straddle | |
|---|---|---|---|
| Cash flow | Debit | Credit | Credit |
| Maximum profit | Width minus debit | The credit | The premium |
| Maximum loss | The debit | Width minus credit | Unlimited |
| Margin | The debit | SPAN and exposure, reduced by the hedge | Full SPAN and exposure |
A long call butterfly and an iron fly with the same strikes have almost the same payoff at expiry. The butterfly uses less margin because you pay for it upfront. The short straddle earns the most at the middle strike but has no limit to its loss.
Automating a butterfly
In QuantPower's strategy builder, a butterfly is four legs with a shared entry rule:
- Set the entry time, such as two days before expiry.
- Buy the lower and higher calls first, then sell the two middle calls.
- Set a target at 40% of the maximum profit and a time exit on expiry day.
Test the rules in paper trading before going live.
Backtesting a butterfly
Test the days to expiry at entry, the width and the centring rule (ATM, highest open interest or max pain). Include realistic slippage for four legs. The average profit per trade after costs matters more than the size of the best wins. See backtesting mistakes for what to avoid.
Frequently asked questions
Why is it called a butterfly?
The payoff chart has a peak in the middle and two flat wings, like a butterfly's body and wings.
Is a butterfly spread profitable?
It has a small, defined loss and a large possible gain, but it wins less often than it loses. Results depend on entry timing and costs.
What is the difference between a butterfly and an iron butterfly?
A long call butterfly uses only calls and costs a debit. An iron fly uses a short straddle with bought wings and collects a credit. The payoffs are almost the same.
How much margin does a butterfly need?
Usually the net debit, because the bought calls cover the sold calls. Some brokers block more. Check before entry.
Sources
- Black, F. and Scholes, M. (1973). The Pricing of Options and Corporate Liabilities. Journal of Political Economy, 81(3), 637–654
- NSE: Equity derivatives contract specifications