What is vanna in options?
Vanna is the rate at which an option's delta changes when implied volatility changes. It is a second-order Greek, which sounds academic, but it matters because a move in volatility alone, with the stock standing still, can change how much stock a dealer needs to hold. That forced re-hedging is what people mean when they talk about vanna flows.
The definition, without the calculus
Delta tells you how many shares an option behaves like. Implied volatility tells you how wide a range of outcomes the market is pricing. Vanna connects the two: if volatility rises by one point, how many shares does the option now behave like? The same number can be read the other way round, as how much an option's vega changes when the stock moves, because the two cross-derivatives are mathematically identical.
The intuition is easiest with an out-of-the-money option. A call struck ten percent above the stock has a small delta because, at the volatility currently priced, there is only a modest chance of finishing in the money. Raise volatility and that chance grows, so delta grows. Lower volatility and the call looks more like a lottery ticket that will expire worthless, so delta shrinks toward zero. Nothing about the stock price changed; only the width of the distribution did.
For an option that is deep in the money the logic runs the other way. A deep in-the-money call behaves almost like stock. Higher volatility raises the chance it falls back out of the money, so its delta drifts down slightly from one. Lower volatility pushes it closer to a full share.
The sign for calls and puts
For a long option, vanna is positive when the strike sits above the stock (roughly, above the forward price) and negative when the strike sits below it. That holds for calls and puts alike, because a put and a call at the same strike and expiry share the same vanna under put-call parity.
Translated into the cases traders actually hold: a long out-of-the-money call has positive vanna, so its delta rises when volatility rises. A long out-of-the-money put has negative vanna, so its delta, already negative, becomes more negative when volatility rises. In both cases higher volatility makes an out-of-the-money option act more like the stock it references, which is the plain-English version of the rule.
Vanna is largest for options a moderate distance from the money and close to zero right at the money, where delta is near fifty and volatility changes shift it very little. It also grows as expiry approaches for strikes near the money, because short-dated deltas are more sensitive to everything.
How vanna becomes stock flow
On its own, vanna is a property of a contract. It becomes a market force through hedging. A market maker who is short an option holds stock to offset that option's delta, so when volatility changes the delta, the hedge has to change too, and that change is a real order in the underlying.
The standard example uses index puts. Under the common assumption that customers are net buyers of downside puts and dealers are net sellers, dealers are short out-of-the-money puts and hold a short stock or futures hedge against them. If implied volatility falls, those puts' deltas shrink toward zero, the dealers are now over-hedged, and they buy back part of their short hedge. Falling volatility therefore produces dealer buying. Rising volatility does the reverse: put deltas grow, dealers need a bigger short hedge, and they sell.
Calls run the opposite way under the same assumption. If customers are long out-of-the-money calls and dealers short them, falling volatility shrinks the call deltas and dealers sell some of the stock they held as a hedge. Which effect dominates depends on where the open interest sits. On broad indices the put side is usually much heavier, which is why the popular shorthand is that a volatility crush supports index prices. On a single stock with heavy call open interest the net effect can point the other way.
Where vanna reasoning breaks down
Every vanna flow estimate inherits the same weakness as every gamma estimate: it depends on assuming which side of each strike the dealer is on. Open interest is public, but ownership is not. If a large share of index puts were actually sold by customers, for example by funds running overwriting or collar programs, the sign of the dealer exposure at those strikes flips, and so does the direction of the flow.
Vanna also does not act alone. Volatility and price tend to move together in equities, falling volatility usually arriving with rising prices, so it is hard to separate a vanna-driven bid from ordinary buying. Treat vanna as a description of why a move in volatility can reinforce a move in price, not as an independent forecast.
Common questions
Is vanna positive or negative for puts?
For a long out-of-the-money put, vanna is negative: higher volatility makes its delta more negative. For a long put struck above the stock, vanna is positive. Calls and puts at the same strike share the same vanna.
What is a vanna rally?
A rally attributed to dealers buying back hedges as implied volatility falls. It assumes dealers are net short downside puts, so falling volatility shrinks the deltas they were hedging. It is an explanation of flow, not a guaranteed pattern.
Is vanna the same as dDelta/dVol?
Yes. Vanna is the sensitivity of delta to implied volatility, which equals the sensitivity of vega to the underlying price.
When does vanna matter most?
When implied volatility moves sharply while large open interest sits out of the money, for example after a scheduled event resolves or in the days around a large expiration.
Vanna is how much delta changes when volatility moves. Under the usual assumption that dealers are short index puts, falling implied volatility forces dealer buying and rising volatility forces selling, but the sign depends entirely on who holds which side.
Keep reading
See it on a live board
FlowMonkey prices every level by whether your ticker can actually reach it today — measured on that symbol's own range, re-sorted as the session burns down.
See pricing