Implied Volatility (IV) and IV Crush Explained
What is implied volatility?
Implied volatility (IV) is the market's expected size of future moves, worked backwards from option prices. You take an option's market price, plug everything else into a pricing model, and solve for the volatility that makes the model match the price. That number is IV.
IV is quoted as an annualised percentage. An IV of 14% on NIFTY means option prices are consistent with NIFTY moving roughly 14% over a year, one standard deviation. It says nothing about direction. It only describes the expected size of moves.
High IV makes options expensive; low IV makes them cheap. Every option trader is, knowingly or not, taking a view on implied volatility.
Approximate move to expiry ≈ Price × IV × √(days to expiry ÷ 365)
Implied vs historical volatility
Historical (realised) volatility measures how much the underlying actually moved over a past window, using the standard deviation of returns. Implied volatility is the forward-looking estimate priced into options.
| Historical volatility | Implied volatility | |
|---|---|---|
| Looks | Backwards | Forwards |
| Source | Price history | Option prices |
| Use | What happened | What the market expects |
When IV sits well above realised volatility, options are pricing more movement than recently delivered. When IV is below realised, options are pricing less. The gap is what option sellers and buyers are effectively arguing about. ATR is a simple way to see realised range on the chart.
Turning IV into an expected move
The formula above converts annual IV into a move over a shorter period. With NIFTY at 24,000 and IV of 13%, the one-day move is about 24,000 × 0.13 ÷ 15.87 ≈ 197 points, one standard deviation.
Roughly two-thirds of the time, under the model's assumptions, the move should stay inside that range. Markets have fatter tails than the model, so large moves happen more often than the bell curve suggests.
A quicker market estimate is the ATM straddle price, which approximates the expected move to expiry directly.
India VIX
India VIX is NSE's volatility index, calculated from NIFTY option prices across near and next-month strikes. It represents the market's expected annualised volatility for NIFTY over the next 30 days.
A rising India VIX usually goes with falling markets and fear; a falling VIX with calm or rising markets. Many traders check VIX before the open to judge whether to expect wide or narrow ranges. It is a gauge of option pricing, not a prediction of direction.
IV crush
What it is
IV crush is the sharp fall in implied volatility after a known event passes. Before the RBI policy, the Union Budget, election results or a company's quarterly results, uncertainty is high and option sellers demand more premium. Once the news is out, that uncertainty disappears and IV falls quickly.
Why it hurts option buyers
An option's price falls by roughly vega times the drop in IV. If an ATM option has vega 10 and IV drops 5 points, it loses about 50 points from IV alone. A buyer can get direction right and still lose because the move was smaller than what IV had priced in. The mechanics of vega are in option Greeks.
Spotting event premium
Compare the IV of the expiry that includes the event with the expiry just before it. A big jump points to event premium that will likely be removed afterwards.
IV percentile and IV rank
Raw IV numbers mean little without context. Two tools help:
- IV rank = (current IV − 52-week low IV) ÷ (52-week high − 52-week low) × 100. It shows where IV sits in its yearly range.
- IV percentile = percentage of days in the past year when IV was lower than today. It is less distorted by one extreme spike.
An IV percentile of 85 means IV has been lower on 85% of days in the past year, so options are relatively expensive. Low readings mean options are relatively cheap.
Volatility skew and smile
IV is not the same for every strike. In index options, out-of-the-money puts usually carry higher IV than equally distant calls, because traders pay up for crash protection. This shape is the skew. When both wings are higher than ATM it is called a smile.
Skew changes with sentiment. A steepening put skew means demand for downside protection is rising. The option chain shows IV per strike so you can see the shape yourself.
Worked example: IV around an event
Illustration with plausible numbers.
Two days before an RBI policy, the BANKNIFTY ATM option's IV is 19% while its usual level is 14%. The ATM straddle prices a move of about 700 points to expiry.
The policy is announced and BANKNIFTY moves 450 points. IV drops to 14%. Even the option on the right side of the move gains less than expected, and the opposite option loses heavily. The straddle as a whole loses value because the realised move was smaller than the priced move.
How option traders use implied volatility
Choosing between buying and selling premium
When IV percentile is low, options are cheap relative to their own history, and some traders prefer strategies that are long volatility. When it is high, options are relatively expensive, and strategies that are short volatility become more common. Neither is safe; this is about what you are paying or collecting.
Choosing expiry
Weekly options carry little vega and a lot of gamma, so they respond mostly to price and time. Monthly options carry more vega, so a change in IV matters more. A trader with a view on volatility rather than direction often looks further out.
Reading the term structure
Comparing IV across expiries shows the term structure. Normally longer expiries have slightly higher IV. When the near expiry has much higher IV than later ones, the market is pricing a near-term event or stress. When the near expiry is far lower, the market is calm now but expects uncertainty later.
Setting realistic targets
The expected move from IV gives a sense of what is a normal day. A 100-point NIFTY target on a day when IV implies a 90-point one-standard-deviation move asks for a larger than average move. Matching targets and stops to the volatility on offer is part of risk management.
Common mistakes with implied volatility
- Reading IV as direction. High IV does not mean price will fall or rise.
- Buying options before events without checking IV. Event premium is often removed afterwards.
- Selling options only because IV is high. IV can rise further in a real crisis.
- Comparing IV across instruments. A stock's normal IV is very different from NIFTY's.
- Ignoring skew. The ATM IV is only one point on the curve.
Seeing it on the TradingMarble chart
The TradingMarble app shows a live option chain alongside the price chart, so you can compare option premiums across strikes and watch how they change around events and expiry. See the features page for details.
Implied volatility checklist
- Check India VIX and the instrument's IV percentile.
- Compare IV with recent realised volatility.
- Look for upcoming events in the expiry you trade.
- Check the skew across strikes.
- Estimate the expected move from IV or the straddle.
- Consider vega before entering any option position.
Implied volatility is the price of uncertainty. F&O trading carries a high risk of loss, and understanding IV and IV crush is basic to understanding what you pay for an option.
Frequently asked questions
What is implied volatility in simple terms?
Implied volatility is the size of future price moves that option prices are currently assuming, expressed as an annual percentage. It is calculated backwards from option premiums. Higher IV means options are pricing bigger moves and are more expensive. It does not indicate direction.
What is IV crush in options?
IV crush is the rapid fall in implied volatility after an expected event such as results, a policy decision or a budget. Because option prices include volatility, the fall reduces premiums even if the underlying moves. It mostly hurts option buyers who entered just before the event.
What is a good IV for NIFTY options?
There is no fixed good value. NIFTY IV has often been in the low to mid teens in calm periods and much higher in stress. It is more useful to compare current IV with its own one-year range using IV percentile or IV rank, and with India VIX.
How is India VIX related to implied volatility?
India VIX is calculated by NSE from the prices of NIFTY options in the near and next months. It represents expected annualised NIFTY volatility over the next 30 days. When NIFTY option IVs rise, India VIX rises with them.
What is the difference between IV rank and IV percentile?
IV rank shows where current IV sits between its 52-week low and high. IV percentile shows the percentage of days in the past year when IV was lower than today. Percentile is less affected by one extreme spike, so many traders prefer it.