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What is Charm?

General Options

Charm (also known as “delta decay”) is the decay of delta with the passage of time. So, Charm measures how much the delta of an option contract changes over time. ATM delta will always be 50, regardless of how near-term the expiration of the contract is. So while Delta indicates how much the option’s price will change for a $1 change in the underlying stock price, Charm tells us how that Delta changes as time progresses.

Charm can be positive or negative. Positive charm means the delta of the option increases as time passes, while negative charm means the delta decreases over time. It's important to note that charm exposure is influenced by changes in implied volatility. High volatility can amplify charm effects, while low volatility may dampen them.