Implied volatility (IV) is the market's forecast of the underlying stock's future volatility, derived from current option prices. Higher IV means options are more expensive. IV is annualized and expressed as a percentage. Premium sellers profit most when IV Rank is elevated; long-option buyers are hurt by IV crush.
IV vs historical, IV rank, IV percentile, IV crush — and how to use volatility to time premium-selling trades.
Implied volatility is the market's forecast of how much an underlying will move over an option's lifetime. It's not historical volatility (what already happened); it's what the market thinks will happen, derived by solving the Black-Scholes equation backward from a quoted option price.
For premium sellers, IV is the single most important number after delta. High IV means rich premiums but also bigger moves you have to survive. Low IV means skinny premiums and quiet markets. Knowing when each regime favors you is the difference between making consistent income and getting blown up by a volatility shock.
IV smile — strike-to-IV curve
Flat-vol assumption (Black-Scholes)Real-world IV curve
Black-Scholes assumes flat volatility (dashed gray). Real markets price OTM puts richer (downside fear) and OTM calls slightly higher than ATM — producing the iconic IV smile / skew.
What implied volatility actually is
Implied volatility (IV) is the annualized standard deviation of the underlying's expected return — implied by the option's market price. It's expressed as a percentage. An IV of 30% means the market expects the stock to move within roughly ±30% over the next year, with normal-distribution probabilities.
IV is forward-looking. Historical volatility (HV) is backward-looking — what actually happened. They are usually correlated but not identical, and divergences between them are a tradable signal.
Some intuitions:
A stock with 60% IV moves about twice as much as one with 30% IV, on average.
An IV of 80%+ usually signals event risk (earnings, FDA decision, merger vote) or genuine distress.
An IV below the underlying's long-run average HV is often a sign the option is cheap to buy.
IV rank vs IV percentile
Raw IV doesn't tell you whether current vol is high or low for this underlying. Two normalizations help:
IV rank = (current IV − 52-week low IV) / (52-week high IV − 52-week low IV). Tells you where current IV sits within its 52-week range. IV rank 80% means current IV is in the top 20% of the past year.
IV percentile = % of trading days in the past 52 weeks where IV was below the current level. IV percentile 80% means current IV is higher than it was on 80% of days last year.
IV rank emphasizes the recent extremes. IV percentile gives a smoother picture. Both are useful; tastytrade popularized IV rank, while other tools use percentile.
For premium sellers: sell premium when IV rank is high (you're getting paid more for the same risk). Wait or roll when IV rank is low.
How to use IV to sell premium
Three practical applications:
Time entries. When IV rank crosses above 50%, scan for income setups. When IV rank is below 30%, hold cash or focus on rolling existing positions.
Size positions. Higher IV means richer premium per contract — you can size smaller and earn the same income. Conversely, low IV requires larger position sizes for meaningful income, which raises tail risk.
Select strikes. In high-IV regimes, you can sell further OTM strikes and still collect meaningful premium. In low-IV regimes, you may need to sell closer-to-ATM to make the trade worthwhile — accept higher assignment risk.
Don't sell premium just because IV is high. The market often prices high IV correctly — earnings, geopolitical risk, or balance-sheet stress are real. Use IV as a filter, not a signal in isolation.
Earnings IV crush
One of the most widely documented IV patterns in equity options: IV typically ramps up in the 1–4 weeks before earnings as uncertainty about the result builds, then usually collapses immediately after the announcement as the unknown becomes known. The magnitude varies by name and quarter — high-guidance and reg-scrutinized names tend to see the largest pre-earnings expansion.
Two classic earnings trades:
Short premium into earnings — sell straddles, strangles, or single-leg short options right before the announcement. Profit from the IV collapse if the stock doesn't move enough to overcome it. Risky: a single big move can wipe out months of theta.
Avoid premium selling through earnings — close positions before the announcement, re-enter after. Sacrifices potential gain for predictability.
For wheel and standard income sellers, the cleanest approach is to time entries so positions don't span earnings. The covered-call calculator can show you the days-to-earnings to flag this.
Volatility regimes and what they mean
The S&P 500's IV (VIX) tells you the overall vol regime. Three rough buckets:
VIX < 15: Low-vol regime. Premium is skinny. Income strategies underperform. Some traders allocate to long-vol hedges or rotate to higher-IV individual names.
VIX 15–25: Normal regime. The premium-selling sweet spot. Most income strategies generate consistent returns.
VIX > 25: High-vol regime. Premiums are rich but moves are large. Position sizing must shrink to compensate. Bad time to be carrying large short-premium exposure into a thesis you're uncertain about.
VIX above 35 typically signals a market dislocation worth respecting. The premium looks irresistible, but the underlying is moving fast enough to negate it. Be patient.
Frequently asked questions
What is implied volatility?
Implied volatility (IV) is the market's forecast of how much an option's underlying will move over the option's life, derived by solving the Black-Scholes equation for volatility given a market price. Higher IV produces richer option premiums.
What's the difference between IV and historical volatility?
IV is forward-looking (what the market expects). HV is backward-looking (what actually happened). They're usually correlated, but divergences are tradable.
What's a good IV rank to sell premium?
Most premium sellers wait for IV rank above 30–50% to enter new positions. Below that, premiums are usually too thin to justify the assignment risk.
What is IV crush?
IV crush is the rapid collapse of implied volatility after a known catalyst (earnings, FDA decision, vote) is resolved. The option's vega component drops dramatically, which lowers the price even if the stock doesn't move.
How do you calculate implied volatility?
By reverse-solving the Black-Scholes equation: given the option's market price, spot, strike, time, and rate, iterate to find the volatility that makes the equation balance. The IV solver on this site does this (delayed ~15 min).
Read more in this series
Deep dives into specific aspects of implied volatility.