Vega Exposure
The total rupee sensitivity of an options position to a one-point change in implied volatility — the aggregate volatility bet embedded in your book.
Definition
Vega exposure is the portfolio-level measure of how much an options position gains or loses in rupee terms for every one percentage-point move in implied volatility. It is computed by summing the individual vega of each option leg, weighted by the number of contracts and lot size. A positive net vega exposure indicates a long-volatility position — the book profits when IV expands — while a negative net vega means the position is short volatility and benefits when IV contracts or remains subdued.
Why it matters
Most retail traders in India focus solely on directional exposure — delta — and underestimate how much their P&L can swing purely from IV changes. On NSE, implied volatility can jump 3–5 points within an hour around RBI announcements, election results, or sudden global macro shocks. A trader holding an unhedged long straddle on Bank Nifty before a policy announcement may have significant positive vega exposure; if the announcement proves uneventful and IV collapses (a classic IV crush), the position loses money even if the underlying moves somewhat. Knowing your vega exposure in rupees — not just as an abstract Greek — forces you to size volatility risk on the same scale as your directional risk, and it becomes the key input when deciding whether to delta-hedge, roll, or flatten the book ahead of a known event.
Formula
Net Vega Exposure = Σ (Vegai × Contractsi × Lot Sizei × Signi)
where Signi is +1 for long legs and −1 for short legs. The result is expressed in INR per 1% move in IV. For example, a net vega exposure of ₹15,000 means the position gains ₹15,000 if IV rises one percentage point and loses ₹15,000 if IV falls one point.
Example
Suppose a trader buys 2 lots of a Nifty 50 ATM call (vega = 0.55 per unit, lot size 75) and simultaneously sells 2 lots of an OTM call at the same expiry (vega = 0.28 per unit). The long leg contributes +0.55 × 2 × 75 = +₹82.50 of vega exposure. The short leg contributes −0.28 × 2 × 75 = −₹42. Net vega exposure is approximately +₹40.50 per 1% IV move. If India VIX jumps 2 points on news, this bull call spread gains roughly ₹81 per spread — a meaningful contributor to total P&L separate from the directional delta gain. The numbers here are hypothetical illustrations only.
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