What is Delta in options trading?


The Delta of an option measures the change in an option contract's price (premium) as a result of a price change in the underlying.

It helps determine the likelihood that an option will expire in the money; strike price below the underlying's market price (for call options) or strike price above the underlying's market price (for put options). For example, if a call option has a delta of 0.30, there is a 30% chance that the option will expire in the money.

The higher the delta, the bigger the price change.

The delta of an option is variable and changes with respect to changes in the price of the underlying and over time.


Call OptionPut Option
Ranges between 0 and 1
Ranges between 0 and -1
Call options have a positive delta as they have a positive relationship with the price of the underlying. If the underlying stock's price goes up and no other pricing variables change, the price of the call will also increase, and vice versa.

For example, a call option has a delta of 0.5. If the underlying stock's price increases by Rs.10, the price of the call will go up by Rs. 5. 
(Delta * Change in underlying)

Similarly, if the stock's price falls by Rs. 10, the price of the call will also decrease by Rs. 5.
Put options have a negative delta and they have a negative relationship with the price of the underlying. If the underlying stock's price goes up and no other pricing variables change, the price of the put will decrease, and vice versa.

For example, a put option has a delta of 0.5. If the underlying stock's price increases by Rs. 10, the price of the put will go down by Rs. 5.

Similarly, if the stock's price falls by Rs. 10, the price of the put will increase by Rs.5.
At the money call options usually have a delta near 0.50.
At the money put options usually have a delta near -0.50.
Delta increases as the call option gets deeper in the money.

As in the money call options approach expiry, delta moves closer to 1.
Delta decreases as the put option gets deeper in the money.

As in the money put options approach expiry, delta moves closer to -1.
Out of the money call options usually have a delta moving close to 0 as expiration approaches.
Out of the money put options usually have a delta moving close to 0 as expiration approaches.

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