What it means
Vega measures how much an option's value changes when implied volatility moves up or down by one percentage point. Long options are long vega; short options are short vega. Vega is highest for at-the-money, longer-dated options.
Why it matters
Volatility regime matters. Buying calls into earnings to express a directional view often loses on vega even if direction is right, because IV crushes after the announcement.
How to use it
Decompose option strategy P/L into delta, gamma, theta and vega. If vega is dominating an unintentional way, restructure. Calendar spreads exploit vega differentials between expirations.
How vega is calculated
Vega is the partial derivative of the option price with respect to implied volatility, scaled to a 1-percentage-point IV move. For an at-the-money call on a $100 stock with 30 days to expiry and 25% IV, vega is roughly $0.10 per share, meaning the option price rises by about $0.10 if IV moves from 25% to 26%. Black-Scholes gives the closed-form value; the Greek itself is rarely computed by hand because every broker platform surfaces it.
Where vega comes from in the term structure
Longer-dated options carry more vega than short-dated ones. A LEAP (1 to 2 year call) on SPY can have vega of $1.20+ per contract per IV point, while a weekly SPY call carries less than $0.10. This is why earnings strategies often pair a long-dated long-vega leg with a short-dated short-vega leg: you isolate the IV crush mechanically.
- Long-dated options: high vega, low gamma, low theta
- Short-dated options: low vega, high gamma, high theta
- At-the-money strikes carry the highest vega; deep OTM/ITM strikes have very little
- Vega is roughly linear in time until the final 30 days, then it accelerates downward
The IV crush trap around earnings
Implied volatility on stocks like NVDA, AAPL, or TSLA can run from 50% to 90% in the week before earnings, then drop 30 to 40 points overnight after the print. A trader who buys ATM calls expecting a 5% post-earnings move can be right on direction and still lose money: the stock moves up 4%, but vega bleed wipes out the gain. This is the most common, most expensive mistake retail option buyers make. The fix is to use vertical or calendar spreads that net out vega.
Vega vs gamma: when each dominates
Vega dominates the P&L of longer-dated, at-the-money options when IV is shifting. Gamma dominates the P&L of short-dated, at-the-money options when the underlying is moving fast. A weekly SPY call going into a Fed meeting may be effectively all gamma; a 6-month QQQ call is mostly vega. Knowing which Greek you are really long determines the catalysts that will pay you. A vega-dominated position needs an IV spike. A gamma-dominated position needs realized vol.
How institutional desks hedge vega
Market makers and vol funds run delta-hedged option books where vega is the residual exposure. They neutralize vega via VIX futures, VIX options, or by buying and selling other options at matched expirations (a vega-matched roll). For retail traders, the simplest hedge is to never take naked vega — pair a long-vega trade with a short-vega trade in the same name, ideally a calendar spread that captures the term-structure differential.
Real-world vega numbers you can sanity-check
Quick reference points for $100-priced underlyings in a 25% IV environment:
- 1-week ATM call: ~$0.04 vega per share
- 1-month ATM call: ~$0.12 vega per share
- 3-month ATM call: ~$0.22 vega per share
- 1-year ATM call (LEAP): ~$0.40 vega per share
- VIX moving from 15 to 25 (10 points) roughly doubles the value of long-vega LEAP positions
Frequently asked
How is vega calculated in Black-Scholes?
Vega equals the underlying price times the standard normal probability density function of d1 times the square root of time to expiry, divided by 100 to scale to a 1-point IV move. In practice every broker platform surfaces it; you rarely compute it by hand.
Does vega change as the option ages?
Yes. Vega decays as expiration approaches, fastest in the last 30 days. A 60-day option loses about half its vega by the time it has 30 days left, and most of the rest in the final two weeks.
What is the difference between vega and gamma?
Vega is sensitivity to implied volatility (what the market expects). Gamma is sensitivity to the underlying price actually moving. Long options are long both, but in different proportions depending on time to expiry.
Why does buying calls into earnings often lose money?
Because implied volatility crushes after the print. A trader can be right on direction but lose to vega bleed if the IV drop outweighs the directional move. The fix is to use vertical spreads, calendars, or buy options in low-IV environments.
Can you hedge vega without selling the option?
Yes. You can short VIX futures, buy VIX puts, or layer in a short-vega leg via a calendar spread or vertical spread in the same underlying at a matched expiration.
What is portfolio vega?
The sum of vega across all option positions in a book, weighted by contract size. Institutional vol funds target a specific portfolio vega (e.g., long 1,000 vega means the book makes $1,000 for each 1-point rise in average IV) and hedge accordingly.
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