Key Takeaway: Implied volatility is the price of uncertainty. High IV means options are expensive — often a better time to sell options than buy them. Low IV means options are cheap — often a better time to buy. The single most important habit you can build is checking IV before entering any options trade.
Implied volatility (IV) is the market's forecast of how much a stock will move, expressed as an annualized percentage. It's called "implied" because it's derived backward from the current option price — it's what the market is implying about future movement.
If a stock has an IV of 40%, the options market is saying: this stock is expected to move 40% over the next year (one standard deviation).
To convert that to a daily expected move, divide by the square root of trading days:
Daily expected move = IV / sqrt(252) = 40% / 15.87 = ~2.5% per day
That's not a guarantee — it's a probability distribution. About 68% of days should fall within that range.
There are two types of volatility traders care about:
Implied Volatility (IV): What options expect will happen. Forward-looking. Set by supply and demand for options.
Historical Volatility (HV): What the stock actually did over some past period. Backward-looking. Calculated from price returns.
When IV > HV, options are expensive relative to what the stock has actually been doing. Option sellers tend to profit over time when IV is structurally elevated above HV — this is called the volatility risk premium.
When IV < HV, options are cheap relative to realized movement. Option buyers get a better deal.
IV is not fixed. It moves constantly based on:
Event risk: Upcoming earnings, FDA decisions, Fed meetings all inflate IV because the event creates uncertainty. The moment the event passes, IV collapses (IV crush).
Market stress: When markets fall sharply, fear spikes and put buying surges. IV across the entire market rises. The VIX is the IV of the S&P 500.
Supply and demand: When a stock has unusual options activity — heavy call buying, unusual positioning — IV rises even without an obvious catalyst.
Time: As expiration approaches with no major catalysts, IV tends to drift toward its normal level.
This is the most practical application:
High IV environment:
Low IV environment:
Most trading platforms show IV next to the option chain. Look for:
A simple rule: if IV rank is above 50%, lean toward selling strategies. If IV rank is below 30%, lean toward buying strategies or debit spreads.
One subtlety worth knowing: IV is not the same across all strikes. Out-of-the-money puts typically have higher IV than OTM calls — this is called volatility skew (or the "smirk").
Why? Because demand for downside protection (puts) is structural. Institutions always buy puts to hedge portfolios. This persistent demand inflates put IV relative to call IV.
What it means for you: puts are almost always more expensive relative to their theoretical value than calls. This is why selling puts (cash-secured puts, short put spreads) tends to collect more premium than equivalent call strategies.