## What Is Delta?

Delta is the ratio that compares the change in the price of an asset, usually marketable security, to the corresponding change in the price of its derivative. For example, if a stock option has a delta value of 0.65, this means that if the underlying stock increases in price by \$1 per share, the option on it will rise by \$0.65 per share, all else being equal.

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## Understanding Delta

Delta values can be positive or negative depending on the type of option. For example, the delta for a call option always ranges from 0 to 1 because as the underlying asset increases in price, call options increase in price. Put option deltas always range from -1 to 0 because as the underlying security increases, the value of put options decrease.

For example, if a put option has a delta of -0.33 and the price of the underlying asset increases by \$1, the price of the put option will decrease by \$0.33. Technically, the value of the option's delta is the first derivative of the value of the option with respect to the underlying security's price.

Delta is often used in hedging strategies and is also referred to as a hedge ratio.

## Examples of Delta

Let's assume there is a publicly-traded corporation called BigCorp. Shares of its stock are bought and sold on a stock exchange, and there are put options and call options traded for those shares. The delta for the call option on BigCorp shares is .35. That means that a \$1 change in the price of BigCorp stock generates a \$.35 change in the price of BigCorp call options. Thus, if BigCorp’s shares trade at \$20 and the call option trades at \$2, a change in the price of BigCorp’s shares to \$21 means the call option will increase to a price of \$2.35.

Put options work in the opposite way. If the put option on BigCorp shares has a delta of -\$.65, then a \$1 increase in BigCorp's share price generates a \$.65 decrease in the price of BigCorp's put options. So if BigCorp’s shares trade at \$20 and the put option trades at \$2, then BigCorp’s shares increase to \$21, and the put option will decrease to a price of \$1.35.

## How Delta Dictates Behavior

Delta is an important calculation (done by computer software), as it is one of the main reasons option prices move the way that they do, and it's an indicator of how to invest. The behavior of call and put option delta is highly predictable and is very useful to portfolio managers, traders, hedge fund managers, and individual investors.

Call option delta behavior depends on whether the option is "in-the-money" (currently profitable), "at-the-money" (its strike price currently equals the underlying stock's price) or "out-of-the-money" (not currently profitable). In-the-money call options get closer to 1 as their expiration approaches. At-the-money call options typically have a delta of 0.5, and the delta of out-of-the-money call options approaches 0 as expiration nears. The deeper in-the-money the call option, the closer the delta will be to 1, and the more the option will behave like the underlying asset.

Put option delta behaviors also depend on whether the option is "in-the-money," "at-the-money" or "out-of-the-money" and are the opposite of call options. In-the-money put options get closer to -1 as expiration approaches. At-the-money put options typically have a delta of -0.5, and the delta of out-of-the-money put options approaches 0 as expiration approaches. The deeper in-the-money the put option, the closer the delta will be to -1.