Learn how vertical debit spreads reshape the Greeks of a long option by selling another strike against it.
Bull and bear direction
A bull call spread normally has positive delta, while a bear put spread normally has negative delta. The short option offsets part of the directional exposure of the purchased leg.
Reduced Greek exposure
Compared with a single long option, the spread commonly has smaller negative theta and positive vega. Its gamma is also reduced because the two legs have opposing gamma signs at the position level.
Changing behavior
As the underlying moves through the strikes, the legs' deltas and other Greeks change at different speeds. Near maximum value, net delta and remaining time exposure can shrink materially.
A practical example
A bull call spread begins at +28 delta with modest negative theta and positive vega. A rally toward the short strike helps, but further upside eventually produces less delta as profit becomes capped.
This simplified example isolates selected sensitivities so their interaction is easier to understand. Live option prices also reflect the underlying price, time decay, rates, dividends, liquidity and transaction costs. Greeks are theoretical estimates, not guarantees.
Frequently asked questions
Why sell the higher strike?
It reduces entry cost and some decay and volatility exposure in exchange for capped upside.
Can a debit spread have positive theta?
It can in some price regions and near expiration, so current net Greeks should be checked.
Is vega always positive?
Often at entry, but it can change as moneyness and time evolve.
Continue the All Greeks in Action cluster
Explore related guides: Option Greeks for Straddles and Strangles · How to Measure Portfolio Option Greeks · How Option Greeks Interact. For a structured sequence, use the free Level 8 – All Greeks in Action course.
Apply the concept: See how these ideas work together in the Bull Call Spread guide, then continue with the free Level 9 course.
Next strategy: Continue with the Butterfly Spread guide and the free Level 12 course.
Options involve risk and are not suitable for every investor. This material is educational and is not investment, tax or legal advice. Greeks are theoretical estimates, and contract terms and broker requirements can vary.