Understand a Bear Put Spread

This guide explains how a bear put spread works on Nifty, the numbers on one lot, how to choose strikes, how it behaves before expiry, how to manage it and how to automate and test it.

At a glance

How a bear put spread works

Buying a put alone profits from a fall, but the whole premium is at risk and time decay works against you. Selling a lower put against it changes the trade:

• The short put's premium reduces the cost, so the breakeven is higher, closer to the current level.
• The profit stops growing below the short strike.
• The maximum loss is the net debit.

The spread suits a view that the index will fall to a particular level. If you expect a crash, a plain long put pays more. For a modest decline, the spread gives a better reward for the risk.

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 25,000 put at ₹227.10
• Sell the 24,700 put at ₹113.40
• Net debit: ₹113.70 per unit, or ₹7,391 per lot

The strikes are 300 points apart. The maximum profit is 300 minus the 113.70 debit, or 186.30 per unit, about ₹12,109 per lot. The maximum loss is the ₹7,391 debit, giving a reward-to-risk of about 1.6 to 1.

The bear put spread is cheaper than the equivalent bull call spread at the same distance, because puts below the market carry less time value than calls above it when interest rates are positive. In the model, the chance that Nifty finishes below the breakeven is about 40%.

Choosing strikes

The long strike

Buy the at-the-money put or one strike in the money. The ATM put has a delta of about −0.46, so the spread responds to the first part of the fall. A put bought further out of the money is cheaper but needs a larger fall before it earns anything.

The short strike

Place the short strike at your target for the index. At 14% IV, one standard deviation of Nifty's move over 12 days is about 635 points, so a 300-point target is a modest move. Falls also tend to lift IV, which makes the long put worth more while the trade is open.

Width of the spread

The wider spread offers more profit per rupee risked, but it needs a fall of 500 points to collect all of it.

How a bear put spread behaves before expiry

The spread's delta at entry is about −0.18 per unit, so a 100-point fall in Nifty adds roughly ₹1,170 per lot at first. Theta is about −₹48 a day per lot with Nifty at 25,000, compared with −₹546 a day for the 25,000 put alone.

With Nifty unchanged after 6 of the 12 days, the position shows a loss of about ₹528. If Nifty has fallen to 24,800 by then, the position shows a profit of about ₹2,816, half of the ₹5,609 it earns at expiry at that level. As with any debit spread, the full value arrives only near expiry, because the short put holds its time value until then.

When a bear put spread works, and when it does not

Works best when:

• You expect a moderate fall to a level you can name.
• IV is low at entry, so the puts are cheap, and rises as the index falls.
• The fall happens early in the trade.

Struggles when:

• The index crashes far below the short strike. The spread earns its maximum, but a plain put would have earned much more.
• The index drifts sideways or rises. The debit decays away.
• The fall comes on the last day. The spread's value then depends on exactly where Nifty settles.

Managing a bear put spread

• Take profits early. Close the spread at 60% to 80% of the maximum profit.
• Set a loss limit. Exit if the spread loses half its debit, or if the index closes above a level that invalidates the view.
• Mind the short strike on expiry day. With Nifty near 24,700, the spread's value swings with every tick.
• Roll down if the fall continues. Close the spread and open a new one at lower strikes if time remains.

Bear put spread vs other bearish strategies

A bear call spread, which sells a call and buys a higher call, profits if the index stays below the short call, even if it does not fall. The bear put spread needs the index to fall past its breakeven.

Using a bear put spread as a hedge

A bear put spread can protect a portfolio of stocks or a long futures position against a moderate fall at a lower cost than a plain protective put. The trade-off is that protection stops below the short strike. For a 300-point spread, the hedge covers a fall of 300 points and no more.

Automating a bear put spread

In QuantPower's strategy builder:

1. Set the entry condition, such as a break below a support level, a moving average cross or a time.
2. Add the long put at the ATM strike and the short put 300 points lower.
3. Place the long leg first so that the broker sees a hedged position for margin.
4. Set a target, such as 70% of the maximum profit, and a stop at 50% of the debit.
5. Add a time exit on expiry day.

Test the rules in paper trading and keep an MTM stop loss across all positions.

Backtesting a bear put spread

Bear spreads are usually entered on a signal rather than on a schedule, because the index rises more often than it falls. Variables to test:

• the entry signal, such as a close below the 20-day moving average or a gap down,
• the long strike, ATM or in the money,
• the width, 200 to 500 points,
• the profit target and stop, and
• whether to exit on a close back above the signal level.

Our guide on how to backtest trading strategies covers the method in detail.

Common bear put spread mistakes

• Buying puts after the fall. IV is then high and the puts expensive, so the spread's reward shrinks.
• Choosing strikes too far out of the money. Cheap spreads rarely pay.
• Holding through a rebound. Set the exit level before the trade.
• Legging in. Buy both legs together as a spread order.
• Ignoring costs. Two legs in and two out, plus STT on the short leg.

Frequently asked questions

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
• SEBI circular SEBI/HO/MRD/TPD-1/P/CIR/2024/132: Measures to strengthen the equity index derivatives framework, 1 Oct 2024