Learn how changes in implied volatility affect both legs of a call debit spread and why net vega is smaller than a long call's.
Net positive vega
At many entries, the lower-strike long call has greater vega than the higher-strike short call, leaving positive net vega. A broad IV rise may help, while a decline may hurt.
Skew matters
The two strikes can trade at different implied volatilities and may not reprice equally. A change in call skew can move the spread even when an average IV number appears stable.
Events and volatility crush
After earnings, both calls may lose extrinsic value. The short call offsets part of that decline, but the price gap and changing deltas can dominate the net result.
Model combined scenarios
Test stock price, time and volatility together. A bullish move with an IV decline can still produce a gain, while a small move may be insufficient after decay and volatility crush.
A practical example
A spread with net vega 0.07 has about +$7 of modeled exposure per IV point per standard spread. A five-point decline implies roughly −$35 before delta, gamma and theta.
This simplified example focuses on the spread at a specific moment and expiration outcome. 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
Does higher IV always help?
Not always; net vega can change and price movement may dominate.
Does the short call remove vega?
It reduces rather than necessarily eliminates vega.
What is skew risk?
The two strikes may experience different IV changes.
Continue the Bull Call Spreads cluster
Explore related guides: Time Decay in a Bull Call Spread · Bull Call Spread Explained: Strategy, Risk and Reward · How to Choose a Bull Call Spread Expiration. For a structured sequence, use the free Level 9 – Bull Call Spread Strategy 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.