What is Theta?
Theta is an options Greek that measures the rate at which an option's value decreases as time passes, assuming all other factors remain constant. Often called time decay, theta represents the cost of holding options over time. For option buyers, theta is an enemy that erodes value daily. For option sellers, theta is a source of profit.
Understanding Theta Values
Theta is typically expressed as the dollar amount an option loses per day. If a call option has theta of minus 5, it loses $5 of value each day, all else being equal. Theta is negative for long options meaning value decreases and positive for short options meaning value decay benefits the seller.
Theta and Time to Expiration
Theta accelerates as expiration approaches. Options lose time value slowly when expiration is far away, then decay accelerates in the final weeks and especially the final days.
Theta and Moneyness
At-the-money options have the highest theta because they have the most time value to lose. Deep in-the-money options have little time value being mostly intrinsic value, so theta is lower.
Managing Theta
Option buyers must be aware of theta drag. Even if you are directionally correct, slow price movement can result in losses as theta erodes value faster than delta gains accumulate.
Strategies to manage theta include buying longer-dated options with lower daily theta, using spreads to offset theta with short options, and timing entries around expected quick moves.
Theta Strategies
Option sellers writing covered calls, cash-secured puts, or more complex strategies benefit from theta. They collect premium upfront and profit as time decay reduces the options' value.