Implied Volatility: What Option Prices Say About Expected Movement

What is Implied Volatility?

Implied volatility is the volatility input that makes an option-pricing model produce the option price observed in the market.

That definition matters because implied volatility is not directly observed like a stock price or option premium. It is backed out from a model.

A trader can observe:

1underlying price
2strike price
3expiration date
4option price
5interest-rate assumptions
6dividend or carry assumptions

Then the trader solves for the volatility input that makes the pricing model fit the option price.

Conceptually:

1Observed option price
2        + pricing model
3        + other model inputs
4        -> implied volatility

CFA Institute describes implied volatility as the Black-Scholes-Merton volatility that yields the market option price. That is why IV is often called a market-implied measure. The market gives you the option price. The model converts that price into a volatility number.

Implied volatility is not historical volatility

Volatility can be measured from past returns. That is usually called historical or realized volatility.

Implied volatility works in the opposite direction. It starts with today's option price and asks what volatility assumption is consistent with that price under a chosen valuation model.

The distinction is:

1Historical volatility -> calculated from past price changes
2Implied volatility    -> inferred from current option prices

Neither number is a guaranteed forecast.

Historical volatility is backward-looking by construction. Implied volatility is forward-looking in the limited sense that option prices incorporate expectations and risk premia about the period before expiration. But the inferred number is still model-dependent and can differ from the volatility that ultimately occurs.

Implied volatility is not an objective forecast of future realized volatility.

A simple implied-volatility example

Suppose a stock trades at $100 and a one-month at-the-money call trades at $4.00.

Assume the option model also uses the strike, expiration, interest rate, and dividend inputs.

If a 20% volatility assumption produces a theoretical option value of only $2.75, while a 35% volatility assumption produces roughly $4.00, then the option's implied volatility is around 35% under that model and those inputs.

The market did not print "35% volatility."

The market printed a $4 option price. The model translated that price into 35% implied volatility.

If the option price rises to $5 while the underlying and other inputs are nearly unchanged, the implied volatility will generally rise too.

That does not mean traders suddenly know the future. It means a higher volatility input is needed to reconcile the model with the richer option premium.

Why more volatility usually makes options more valuable

A long option has asymmetric payoff.

For a call, the downside to the buyer is limited to the premium, while larger upside moves can increase the payoff. For a put, large downside moves in the underlying can increase the payoff while the buyer's loss remains capped at the premium.

Greater uncertainty about the future price therefore tends to increase the value of optionality.

That intuition is captured by Option Vega, which measures an option's local sensitivity to a change in implied volatility.

The relationship is not a prediction that the underlying will move in a particular direction. Higher IV says the option market is pricing more uncertainty or paying more for optionality, not that the stock is expected to rise.

There is no single implied volatility for a stock

It is common to hear statements such as "the stock's IV is 40%."

That shorthand can be useful, but the option chain usually contains many implied volatilities.

Different options can have different:

• strikes;
• expiration dates;
• call or put characteristics;
• liquidity;
• bid-ask spreads; and
• supply and demand.

As a result, an underlying can have a full implied-volatility surface rather than one universal number.

Across strikes for the same expiration, the pattern is often called a volatility smile or skew. Across both strike and expiration, it becomes a surface.

CFA Institute notes that if the Black-Scholes-Merton assumptions held perfectly, the volatility surface would be flat. Real markets do not behave that way.

Why strike matters

Out-of-the-money puts on an equity index often carry different implied volatility from equally distant out-of-the-money calls.

One reason is that investors may pay more for downside protection. Another is that the actual distribution of returns is not perfectly described by the simple lognormal assumptions embedded in basic option models.

The result is that "25% implied volatility" on one strike is not automatically comparable with "25% implied volatility" on another without looking at maturity, moneyness, and the market being priced.

Option Moneyness provides the basic vocabulary for those strike relationships.

Why expiration matters

Implied volatility can also differ sharply across maturities.

Imagine a company reports earnings in ten days.

A two-week option includes that event. A three-month option includes the event too, but spreads its effect across a much longer period. The implied volatilities can therefore differ even when both contracts reference the same stock.

This pattern across expirations is often called the volatility term structure.

Short-dated event volatility can become especially elevated before earnings, regulatory decisions, product announcements, court rulings, or macroeconomic releases.

What a volatility crush means

A volatility crush is a sharp decline in implied volatility, often after an uncertainty-producing event passes.

Suppose a trader buys a call before earnings because the trader expects the stock to rise.

The stock does rise after the announcement, but less than the option market had priced. At the same time, the uncertainty around earnings disappears and implied volatility falls sharply.

The call can lose value even though the stock moved in the expected direction.

Why?

Because option value changed through more than one input:

1underlying-price effect -> captured locally by delta
2volatility effect       -> captured locally by vega
3time passage            -> captured locally by theta
4curvature                -> captured locally by gamma

The Greeks interact. Looking only at direction can miss much of the trade.

Implied volatility and expected move are related but not identical

Traders often convert implied volatility into a rough expected-move range.

A common scaling intuition is:

1Expected one-standard-deviation move
2≈ Price × annualized IV × sqrt(time in years)

For a $100 stock with 36% annualized IV and one month remaining:

1100 × 0.36 × sqrt(1/12)
2≈ $10.39

That arithmetic can be useful for intuition, but it rests on strong distribution and annualization assumptions.

It does not mean the stock has a 68% guaranteed probability of staying within exactly that range. Real returns can be skewed, fat-tailed, discontinuous, and event-driven.

An option chain also contains different IVs by strike, so the expected-move shortcut compresses a richer surface into one number.

Implied volatility contains risk premia

Option prices are not just neutral forecasts of realized movement.

Option sellers demand compensation for bearing risk, capital usage, adverse selection, jump risk, hedging difficulty, and other costs. Buyers may pay a premium for insurance-like convexity.

That means implied volatility can systematically differ from future realized volatility.

In some markets and periods, implied volatility has often exceeded subsequently realized volatility. That gap is one reason volatility-selling strategies can earn a premium, but it is not free money. The premium can compensate for rare, severe losses and difficult hedging conditions.

A persistent historical gap does not guarantee the same trade will remain profitable.

Implied volatility depends on the model

The same option price can imply somewhat different volatility under different models or implementation choices.

Important choices include:

• European versus American exercise treatment;
• dividend assumptions;
• interest rates and funding curves;
• discrete versus continuous dividends;
• underlying forward price;
• numerical solver choices; and
• treatment of early exercise or settlement conventions.

For simple European options, Black-Scholes-Merton remains a common reference model. American equity options often require binomial or other methods that handle early exercise.

This is another reason IV should not be treated as a raw market fact independent of methodology.

Bid-ask spreads can create an IV range

An option may be quoted at:

1Bid: $3.80
2Ask: $4.20

The implied volatility calculated from the bid will differ from the IV calculated from the ask.

A platform may show IV based on the midpoint, last trade, bid, ask, or another mark.

For thinly traded contracts, those choices can materially change the displayed number.

A precise-looking IV such as 37.42% can therefore overstate the precision of the underlying market information.

Implied volatility is not the VIX

The VIX is a specific Cboe index constructed from S&P 500 option prices across a prescribed set of strikes and maturities to represent a 30-day forward-looking volatility measure.

An individual option's implied volatility is different.

VIX is an index methodology applied to a basket of SPX options. IV is generally the model-implied volatility associated with a particular option quote or a summarized section of an option chain.

The concepts are related, but they are not interchangeable.

How investors should read implied volatility

When comparing IV, ask:

1. Which underlying does the option reference?
2. What strike and expiration are being used?
3. Is the option a call or put?
4. Is the displayed number based on bid, ask, midpoint, or last trade?
5. Which pricing model and dividend assumptions are used?
6. Is the contract American or European style?
7. How does current IV compare with the same contract's history?
8. How does IV vary across strikes and maturities?
9. Is a known event inside the option's life?
10. How does implied volatility compare with subsequently realized volatility?

Grizzly Bulls' Models can be evaluated with these questions without turning this page into a live options engine. The broader Indicators library can supply market context, but it does not define an option's implied volatility or volatility surface.

Sources and further reading

• CFA Institute, 2026, Pricing and Valuation of Options: https://www.cfainstitute.org/insights/professional-learning/refresher-readings/2026/pricing-valuation-options
• CFA Institute, 2026, Valuation of Contingent Claims: https://www.cfainstitute.org/insights/professional-learning/refresher-readings/2026/valuation-contingent-claims
• Cboe Options Institute, Options Calculator: https://www.cboe.com/oi/tools/options_calculator/
• The Options Industry Council, May 2026 Office Hours FAQs: https://www.optionseducation.org/news/may-office-hours-faqs

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