What Vanna and Charm Are
Most traders stop at the first-order Greeks — delta, gamma, theta, vega. But dealer delta isn't a fixed number. It drifts as the market moves, as implied volatility changes, and as time simply passes. Vanna and charm are the second-order Greeks that describe how a dealer's delta shifts along those two axes — volatility and time.
Vanna measures how delta changes when implied volatility moves. Charm — sometimes called delta decay — measures how delta changes as time passes toward expiration. Both sit one layer beneath gamma: where gamma exposure (GEX) tells you how dealer delta reacts to spot movement, vanna and charm tell you how it reacts to the two variables spot doesn't capture.
Charm = ∂Delta / ∂Time
Vanna: the rate of change of delta per 1% move in implied volatility
Charm: the rate of change of delta per day of elapsed time
Both are second-order — derivatives of delta, one step past gamma.
The elegant symmetry of vanna is worth pausing on: because delta and vega are both first derivatives of the option price, the cross-partial is the same whether you differentiate delta by volatility or vega by spot. That's why vanna = ∂Delta/∂IV = ∂Vega/∂Spot — one number describes two seemingly different sensitivities.
Why Dealers Care
Options market makers run delta-neutral books. Every contract they hold against customer flow carries a delta, and they hedge it by trading the underlying — the mechanism explained in delta hedging and dealer flows. The catch is that the delta they're hedging is a moving target.
Gamma captures the movement driven by spot. But two other forces shift dealer delta without spot moving a single tick: a change in implied volatility (vanna) and the simple advance of the clock (charm). When either of those forces moves dealer delta, market makers must re-hedge — buying or selling the underlying to return to neutral. That re-hedging is a real, predictable flow, and it's precisely what vanna and charm exposure quantify.
The hierarchy of dealer flows. Spot moves drive gamma hedging (first-order). Volatility changes drive vanna hedging, and time passing drives charm hedging (both second-order). Gamma dominates on a normal trading day — but around large volatility shifts and into expiration, vanna and charm can become the primary flow.
Vanna: Delta Shifts With Implied Volatility
Vanna answers a specific question: if implied volatility rises or falls, which way does dealer delta move, and by how much? Because dealers are typically short vega against customer demand for protection, a volatility spike can force meaningful directional re-hedging even when the underlying hasn't moved.
Consider a classic setup. Dealers are short downside puts to customers who bought them for protection. As implied volatility falls — say a feared event passes without incident and IV compresses — the delta of those short puts changes, and dealers must buy the underlying to stay neutral. This is the mechanical engine behind the well-documented "vanna rally": falling volatility mechanically pulls dealer hedging flows in a supportive direction.
On greeks.pro this is measured as VEX — vanna exposure. The endpoint aggregates each strike's vanna against its open interest to produce a net figure: how much dollar delta the dealer complex must re-hedge for every 1% move in implied volatility.
Reading vanna in practice: A large positive net VEX means a rise in implied volatility forces dealers to buy the underlying, while an IV drop forces selling. Pair it with the direction of the current volatility regime — VEX only tells you the flow that IV changes will trigger, not the direction IV will take.
Charm: Delta Decay, OPEX and End-of-Day Drift
Charm is the quiet Greek. Nothing needs to happen in the market for it to act — the passage of time alone reshapes dealer delta. As options approach expiration, their deltas migrate: in-the-money options drift toward a delta of 1 (or −1), and out-of-the-money options decay toward 0. That migration forces continuous, low-key dealer re-hedging.
Two well-known market patterns are charm-driven. The first is OPEX drift — the tendency for markets to grind in a consistent direction into monthly options expiration as large open interest positions decay and dealers unwind the associated hedges. The second is end-of-day drift, where the accumulated charm of the day's contracts pulls hedging flows in the final hour toward the close.
Charm accelerates into expiration. Delta decay is small far from expiry and grows rapidly in the final days — the shorter the time to expiration, the faster delta migrates. This is why OPEX and end-of-day charm flows concentrate their impact right before contracts expire, not weeks ahead.
How to Read VEX on greeks.pro
The /api/analytics/vex endpoint (available on Pro and above) computes vanna and charm exposure across the full options chain. It returns two headline figures plus a per-strike breakdown, all derived from live options chains using Black-Scholes Greeks with a continuous dividend yield.
| Field | Meaning |
|---|---|
| totalNetVEX | Net dollar delta shift per 1% move in implied volatility across the whole chain |
| totalNetCharm | Net dollar delta shift per day from the passage of time alone |
| callVEX / putVEX / netVEX | Per-strike vanna exposure — call, put, and net |
| callCharm / putCharm / netCharm | Per-strike charm exposure — call, put, and net |
Interpretation follows the mechanics directly. A large net VEX means an IV move forces dealers to re-hedge directionally — the bigger the number, the more the volatility regime matters to price. A large net Charm means the mere passage of time forces re-hedging, which is what drives OPEX drift and end-of-day drift. Both are second-order effects that sit behind gamma and GEX.
Sign convention. In the VEX calculation, put vanna exposure is signed negative — putVEX = −(put vanna × put OI × 100 × spot) — while call VEX is positive. The net figure combines both sides so you read a single directional number for the dealer complex.
Putting It Together With GEX
Vanna and charm are most useful read alongside gamma exposure, not in isolation. GEX tells you how dealers react to spot movement — whether they dampen or amplify moves. VEX and charm tell you the flows that spot movement doesn't explain: what happens when volatility shifts and what happens simply because time is running out.
The three layer into a coherent picture. On a calm day inside positive gamma, GEX pins price and second-order flows are background noise. But when a volatility event hits, vanna can dominate — a sharp IV move forces dealer re-hedging that overrides the gamma pin. And into a monthly expiration, charm quietly accumulates until OPEX unwinds it in a directional drift. Reading all three together — gamma, vanna, and charm — is what separates a first-order view of dealer positioning from a complete one.