Every quarter, thousands of retail option buyers in India make the same mistake: they buy a long straddle the day before earnings, convinced that "the stock will definitely move." The stock moves. And they still lose money. This is IV crush in action, and Vega is the Greek that explains it.
This guide shows the exact math of Vega, walks through three real earnings trades (RELIND, TCS, HDFCBANK), and explains why professional volatility traders sell events rather than buy them.
1. Vega — The Volatility Greek
Vega tells you how much your option price changes when implied volatility changes by 1 percentage point. Unlike Delta (direction) and Theta (time), Vega is purely about the market's expectation of future volatility.
The one-line definition
Vega = change in option price per 1% change in IV. Long options have positive Vega (you benefit when IV rises). Short options have negative Vega (you benefit when IV falls). Vega is highest for ATM options with longer DTE.
IV itself is forward-looking — it is the market's collective guess about how much the stock will move in the future. Before earnings, IV is elevated because uncertainty is high. After earnings, IV collapses because uncertainty is resolved.
2. Why IV Crush Happens — The Mechanics
TCS IV Behavior Around EarningsHistorical pattern
| Day | TCS Spot | ATM IV | ATM Straddle |
|---|
| T-14 (normal) | ₹3,880 | 20% | ₹95 |
| T-7 | ₹3,870 | 28% | ₹125 |
| T-3 | ₹3,875 | 36% | ₹155 |
| T-1 (earnings day) | ₹3,880 | 45% | ₹180 |
| T+1 (post-earnings) | ₹3,920 | 22% | ₹88 |
| T+7 | ₹3,925 | 19% | ₹52 |
Notice IV climbing from 20% to 45% in 14 days before earnings, then collapsing to 22% in a single overnight. This is IV crush.
3. TCS Earnings — The ₹42k Loss
Example · Retail trader buying a straddle
BUY 3880 CE + BUY 3880 PE at ₹180 combined (T-1)
Total cost: ₹180 × 175 lot = ₹31,500. Trader thinks "earnings always move TCS."
TCS earnings release: beats estimatesStock +1% to ₹3,920
Call side (3880 CE)Value: ₹52 (gained ₹12 from direction)
Put side (3880 PE)Value: ₹36 (lost ₹59 from direction + vega)
Combined value post-earnings₹88 × 175 = ₹15,400
Loss₹-16,100 (51% of capital)
TCS moved in the buyer's favor (+1%) but they still lost 51% of capital because IV crushed from 45% to 22%. Vega cost them ~₹23,000 — more than direction could compensate.
4. RELIND Earnings — Selling the Event
Example · Pro trader selling IV
SELL 1310 CE + SELL 1310 PE at ₹65 combined (T-1)
RELIND at ₹1,310, IV at 38% before results. Pro trader collects ₹65 × 500 lot = ₹32,500 premium. Defined-risk wings added.
RELIND reports: slight missStock -0.8% to ₹1,298
IV crashes 38% → 22%Straddle value drops to ₹28
Buy-to-close next day₹28 × 500 = ₹14,000
Profit+₹18,500 (57% of max)
Same event, opposite side of the trade. Pro trader pocketed ₹18,500 because IV crushed faster than the stock moved. This is how event-sellers consistently earn in Indian option markets — sell inflated IV, close after the crush.
5. HDFCBANK — Budget Day Trade
Example · Budget day volatility play
HDFCBANK at ₹1,620. IV ran from 18% → 32% in budget week.
Pro trader sells a 1600/1640 iron condor for ₹22 net credit, lot 550, total credit ₹12,100.
Budget released, no banking surprisesHDFCBANK +0.4% to ₹1,626
IV crashes 32% → 19% in 2 hoursIron condor value ₹8
Close 2 hours after budgetCost to close: ₹4,400
Profit+₹7,700 (64% of max) in 2 hours
Pure IV crush play. Direction didn't matter — only that IV reverted to baseline. Pros routinely target these known-catalyst events (budget, RBI policy, election results, earnings).
6. How Pros Trade Events — The Rules
Rule 1: Check IV Rank before any earnings trade. Only sell vol when IV Rank > 50%. Only buy vol when IV Rank < 20%.
Rule 2: Use defined-risk structures. Iron condors, not naked short strangles. A single Maruti-style 15% post-earnings move can blow up a naked seller.
Rule 3: Close within 24 hours of event. Target 50% of max profit. Don't hold for the last 10% — gamma plus surprise news can reverse your position fast.
Rule 4: Size small. Earnings trades are high-variance. Max 1-2% of capital per trade. Professionals accept that 30-40% of earnings trades lose — but the expected value is positive over 50+ trades.
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Frequently Asked Questions
What is Vega in options trading?
Vega measures how much an option's price changes for a 1% change in implied volatility (IV). If an option has Vega 8, a 1% rise in IV increases the option price by ₹8. Vega is always positive for option buyers — you benefit when uncertainty rises. It is negative for sellers.
What is IV crush?
IV crush is the sudden drop in implied volatility that happens after a scheduled event like earnings, RBI policy, or budget announcement. Before the event, uncertainty is high and IV is inflated. Once the event is over, uncertainty disappears and IV collapses, often by 30-50% in hours. This crushes long option positions regardless of direction.
Why do straddles lose money before earnings?
Because you're buying inflated volatility. A TCS ATM straddle before earnings might cost ₹180 when IV is 45%. After earnings, even if TCS moves 4% (matching the implied move), the straddle often drops to ₹90 because IV crashes to 25%. The directional gain is eaten by vega loss. This is one of the most common retail option traps in India.
Should I sell options before earnings?
Selling inflated IV can be profitable but risky. A short straddle or iron condor before earnings benefits from IV crush, but you're exposed to any large directional move. Professional traders do this only with defined-risk structures (iron condors) and strict position sizing — typically 1-2% of capital per trade.
How is Vega different from Theta?
Theta measures decay per day of time passing. Vega measures decay per percentage point of IV change. Both erode long option positions, but for different reasons. A long straddle held through earnings might lose 20% from theta over 7 days — and another 40% from vega in 10 minutes when IV crashes post-event.
When is vega risk highest?
Vega risk is highest for long-dated options, ATM options, and options ahead of known events. A 45-DTE ATM NIFTY call has ~3x the vega of a 7-DTE equivalent. Before budget, election results, or major company earnings, vega can dominate Greek exposure — making IV awareness more important than direction.
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