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L.8 · BEGINNER · 3 MIN

Vega in Depth: What You Are Really Paying for Volatility

Delta, theta and gamma all connect to things you can see: the stock moved, or the calendar advanced. Vega connects to something invisible — the market's opinion about how much the stock is likely to move from here. That opinion is implied volatility, and it is an input to every option price on the board. When it changes, every premium re-prices even though the chart is flat and no time has passed. Vega is how much of that re-pricing lands on your contract. Ignore it and you will eventually experience the most disorienting outcome in options: being right about the direction, watching the stock gap your way, and finding the position worth less than it was the night before.

Quiz · 1 question ↓

Vega grows with time to expiration

At-the-money call on a $100 stockApproximate vegaIf implied volatility rises 5 pointsIf implied volatility falls 5 points
7 days to expiration$0.06about +$0.30about −$0.30
30 days to expiration$0.11about +$0.55about −$0.55
90 days to expiration$0.20about +$1.00about −$1.00
One year to expiration$0.40about +$2.00about −$2.00

What vega measures, and which side you are on

Vega is dollars per point. It is the change in an option's price for a one-percentage-point change in implied volatility, holding the stock and the calendar still. Buyers are long vega on both calls and puts, because a wider expected range makes any option more likely to be worth something; writers are short vega for the mirror reason. Notice what the table above says about time: vega scales UP with the remaining life of the contract, which is the opposite of theta's shape. A weekly contract barely notices a volatility move; a one-year contract is dominated by it. That single contrast explains why short-dated trades are theta stories and long-dated trades are volatility stories, and why matching the instrument to the thesis matters more than picking a clever strike.

Reading vega on a quiet day

You own a 90-day at-the-money call with a vega of $0.20. Implied volatility falls 4 points overnight and the stock closes unchanged. What happened to the option?

Walking through an earnings-week volatility collapse

Set the scene the night before a scheduled earnings report. The market knows a large move is coming but not which way, so implied volatility on the near-dated strikes is bid up hard. Our trader buys an at-the-money weekly call for $3.00. Delta is 0.50, vega is $0.06 (the 7-day row of the table above), and implied volatility is about 55%, far above where it traded a month ago.

The print lands and the stock gaps up $2 — a genuinely correct directional call. Delta credits the position with roughly 0.50 × $2 = $1.00 per share. So far the trade is working exactly as intended.

Caution: Then the volatility side settles up. With the uncertainty resolved, implied volatility collapses by 30 points. Vega bills the position $0.06 × 30 = $1.80 per share. Netting the two effects: $3.00 + $1.00 − $1.80 = $2.20. The call is worth about $2.20 against the $3.00 paid, and almost all of what is left is the $2.00 of intrinsic value.

Caution: This is the IV crush. The trader was right about direction, right about the magnitude being meaningful, and still lost about a quarter of the premium, because the volatility they bought was mathematically certain to deflate once the event passed. The buyer of an event-week option is paying peak retail for a component with a known expiry date.

Pricing the crush

A trader buys an at-the-money weekly call for $3.00 the day before earnings. Delta is 0.50 and vega is $0.06. The stock gaps up $2 on the print and implied volatility collapses 30 points. Roughly what is the call worth now?

Price an earnings-week IV collapse

Pick a company you follow and find when it usually reports: its earnings releases are filed with the SEC on Form 8-K (Item 2.02), so the last few filings show its calendar. Then price the event with the vega table above. On a $100 stock, a 20-point IV collapse costs a weekly at-the-money call about $1.20 ($0.06 × 20), while a $2 move earns a 0.50-delta call about $1.00. If the collapse you expect is bigger than the move you expect, an event-week call loses even when you are right about direction.

Who is on which side of a volatility move

Two investors look at the same at-the-money call. One is long it, the other wrote it. Implied volatility rises 4 points overnight and the stock is unchanged. Vega is $0.15. Who gains?
Check your understanding

Sit with the ideas.

You hold a 90-day at-the-money call with a vega of $0.20 and a delta of 0.50. Overnight the stock is unchanged but implied volatility falls 6 points. What happens to the option?

Why:
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Other lessons in this course.

  1. 01Calls and Puts: The Building Blocks
  2. 02Options P&L: Calculating Profit and Breakeven
  3. 03Moneyness, and Reading Delta as Probability
  4. 04The Four Greeks: Delta, Theta, Gamma, and Vega
  5. 05Delta: Direction, Odds, and Share-Equivalent Exposure
  6. 06Theta in Depth: How Time Decay Actually Bleeds an Option
  7. 07Gamma in Depth: The Curvature That Moves Delta
  8. 08Vega in Depth: What You Are Really Paying for Volatility— reading now
  9. 09Implied Volatility: The Options Market's Forecast
  10. 10Covered Calls, Cash-Secured Puts, and Protective Puts
  11. 11Intrinsic vs Time Value: The Two Halves of Every Premium
  12. 12Assignment, Exercise, and the Early-Exercise Surprise
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