Unit 10 of 15 · Intermediate

Vega and implied volatility

In one read

Implied volatility (IV) is the market's expectation of how much the underlying will move, backed out of an option's premium — a fear-and-demand gauge, not a forecast of direction. Vega is the greek that measures exposure to it: how much an option's price changes when IV moves one percentage point. Both a call and a put gain value when IV rises, because more expected movement makes the right to transact more valuable, and both lose value when IV falls. This is why you can be right on direction and still lose: buy an option into an event when IV is high, see the stock move your way but less than the priced-in amount, and the IV collapse can outweigh the directional gain. This unit reads vega on the same generic at-the-money call from the delta, gamma, and theta units, so volatility becomes a position you hold, not weather that happens to you.

IV is the market's expected move; vega is your exposure to it

Implied volatility (IV) is the market's expectation of how much the underlying will move, read backwards out of the option's premium. It is a gauge of expected magnitude, not direction — often called the market's fear gauge because it swells when the crowd pays up for protection and demand for options rises.

Vega is the greek that measures your exposure to IV: how much an option's price changes when IV moves one percentage point.

The direction is the same for both contract types:

  • When IV rises, both calls and puts gain value — more expected movement makes any right to transact worth more.
  • When IV falls, both lose value.

That symmetry is the whole reason vega is its own risk. Delta cares which way price goes; vega only cares how much the market expects it to move.

A worked example

Same GENCO $100 call we read for delta, gamma, and theta — ATM, a month out. Say its vega is $0.12 per IV point, and IV currently sits at 30%.

  • IV climbs from 30% to 34% (say, into an announcement): the call gains about 4 × $0.12 = $0.48 from vega alone — before the stock moves at all.
  • IV falls from 30% to 24% afterward: the call loses about $0.72 from vega.

Here is the trap the greek exists to name. Buy that call into a high-IV event, watch GENCO move your way but by less than the market had priced in, and the IV collapse through vega can outweigh the delta gain — you were right on direction and the position still fell. Being right on the stock is not the same as being right on the volatility you paid for.

See it in kestrel

Vega lives in changing volatility, so it is clearest against a session where IV would be moving hard. Run one and watch the volatility regime shift:

npx kestrel.markets sim s-p-500-etf-pandemic-volatility-crash

That runs a deterministic simulation over a generic broad-ETF session with a real volatility surge and collapse — managed licensed data, no wall time, no signup, no card — and prints a certified proof URL. Because the volatility is on the recorded tape, the way an option's vega exposure would swing is something you recompute, not guess. Run it again on your own machine, byte for byte:

npx kestrel.markets certify https://kestrel.markets/proof/art_66d7dda7f0466f69c123463c

Keep the volatility one command away: drop the kestrel.markets MCP server into your client and the next session opens where this one left off — no account in between.

Recompute it

Every claim in this unit recomputes from a certified proof — no account, no card.

/proof/art_66d7dda7f0466f69c123463c
Keep readingThe anatomy of a 0DTE day

Agent twin: /education/options/opt-vega-and-iv/content.md