The index long put is the simplest strategy to use in index options trading and the implementation involves the purchase of an index put option.
Buy 1 put.
The options trader employing the index long put strategy believes that the underlying index level will fall significantly below the put strike price within a certain period of time.
Profit potential
Profit is bounded for the stated stock/index position.
Strike price minus the premium paid, if the stock falls to zero.

Loss potential
Loss is finite under the stated assumptions, but can be substantial. A stock or nonnegative index cannot fall below zero.
The premium paid.
Breakeven points
Strike price minus the premium paid, provided the result is zero or above.
Example
XYZ Index is a broad based index representative of the entire stock market and its value in June is 400. Believing that the broader market will retreat in the near future, an options trader purchases an six-month XYZ index put with a strike price of $400 expiring in December for a quoted price of $4.00 per contract. With a contract multiplier of $100, the cost of the index put option comes to $400.
Suppose XYZ Index dropped to 380 in December and the trader's DEC 400 XYZ index put expires in-the-money. At settlement value of 380, the DEC 400 XYZ index put option will have an intrinsic value of $20 and exercising this option will give the trader a settlement amount of $2000 ($20 x $100 contract multiplier). Taking into account the cost of the option itself, which is $400, the trader's net profit comes to $1600.
Suppose XYZ Index went up to 420 in December and the trader's DEC 400 XYZ index put expires out-of-the-money. At settlement value of 420, the DEC 400 XYZ index put option will expire worthless with zero intrinsic value. The trader's net loss is equal to the amount paid for the index put option which is $400.
Commissions
These examples exclude commissions and fees. Include all transaction costs when evaluating the profit or loss of a position.
Out-of-the-money Index Puts
Going long on out-of-the-money puts maybe cheaper but the put options have higher risk of expiring worthless.
In-the-money Index Puts
In-the-money puts are more expensive than out-of-the-money puts but less amount is paid for the option's time value.
Portfolio Insurance
Index puts can also be used to protect a portfolio against a declining market without the need to liquidate any stock while at the same time enable the portfolio to participate and benefit from a rising market.
Amounts are in index points before fees. Multiply by the contract multiplier to convert them to money. If a maximum profit or loss calculation gives a negative amount, use zero. These figures assume matching contracts held to expiration and do not include financing or early assignment.
Financial mechanics reviewed:
Sources: OIC strategy reference; OIC assignment guidance. Formulas use the stated payoff assumptions; examples are illustrative, not market quotes. Editorial standards and corrections.