Volatility and the VIX: historical vs implied volatility explained

Volatility is how much and how fast a price moves. It is the raw material of risk: it sets how wide a stop has to be, how big a position can be for a given risk budget, and how much an option costs. Traders talk about it in two ways. Historical volatility measures how much prices did move. Implied volatility is the amount of movement that option prices suggest the market expects.

The best-known measure of implied volatility is the Cboe Volatility Index (VIX), often called the market's "fear gauge". This page explains the two kinds of volatility, how the VIX is calculated, what its history since 1990 shows, including its spikes in 2008 and 2020, and why products linked to the VIX don't behave like the index itself. It is educational; nothing here is a forecast or a suggestion to trade volatility.

Historical volatility: what prices did

Historical volatility, also called realized volatility, is a statistic computed from past prices. The standard recipe takes daily returns (usually log returns, the natural log of today's close divided by yesterday's), computes their standard deviation over a window such as 21 or 63 trading days, and annualizes it.

Annualizing lets volatilities measured over different windows be compared, and puts them on the same scale as implied volatility. It also assumes that returns are independent from day to day, which real markets violate, especially in a crisis.

Historical volatility is precise but backward-looking. It tells you what kind of moves a stock has made, not what it will do next. The Average True Range used for stops in Stop-loss placement: volatility, structure and time stops is a close cousin: also backward-looking, but expressed in dollars of daily range rather than as an annualized percentage.

Implied volatility: what option prices expect

An option's price depends on several inputs: the stock price, the strike, the time to expiration, interest rates, dividends and volatility. All but the last are observable. Implied volatility is the volatility figure that, plugged into an option-pricing model, reproduces the option's market price. It is the market's price for uncertainty, read in percentage terms.

Implied volatility rises when traders pay more for options, typically because they want protection or expect large moves (an upcoming earnings report, a central-bank decision, a sell-off already under way). It falls when demand for protection fades. Each strike and expiration has its own implied volatility, so a single stock has a whole surface of them.

What the VIX measures

The VIX turns the implied volatility of the S&P 500 options market into one number. According to Cboe's methodology, the index "is designed to measure the market's expectation of 30-day forward looking volatility" of the US equity market as conveyed by S&P 500 option prices.

A short history of the index

• 1993. Cboe introduced the VIX. The original version measured 30-day implied volatility from at-the-money options on the S&P 100 (OEX).
• 2003. Cboe and Goldman Sachs updated the methodology. The current VIX is based on the S&P 500 and aggregates the weighted prices of SPX puts and calls across a wide range of strikes, not just at-the-money options.
• 2004 and 2006. VIX futures began trading on March 26, 2004 on Cboe Futures Exchange, and VIX options followed in February 2006.

Cboe publishes daily VIX values back to January 1990, before the launch, calculated retroactively; the history used on this page starts there.

How it is calculated, in outline

Cboe's methodology document sets out the full math. In outline:

1. Pick two expirations around 30 days. The index uses standard monthly SPX options and weekly SPXW options, and selects a near-term and a next-term expiration that bracket a constant 30-day horizon.
2. Use out-of-the-money puts and calls. For each expiration it takes the mid-quote (halfway between bid and ask) of out-of-the-money options with non-zero bids, across a strike range Cboe determines, centered on an at-the-money strike.
3. Combine them into a variance. The option prices are weighted and summed into an estimate of expected variance for each expiration, using US Treasury yields as the interest-rate input.
4. Interpolate to 30 days and convert. The two variances are interpolated to exactly 30 days, and the square root, times 100, is the VIX.

Because it is built from options across many strikes, the VIX reflects the price of crash protection (out-of-the-money puts) as well as ordinary at-the-money volatility.

Reading the number

The VIX is quoted in annualized percentage points. Dividing by √12 gives a rough one-month, one-standard-deviation move in the S&P 500; dividing by √252 gives a daily one.

Two caveats matter. The VIX describes the S&P 500 index, not any individual stock, which is usually more volatile. And it is a market price, so it includes what traders are willing to pay for protection, not just a neutral forecast.

Implied versus realized: the gap

Implied volatility has tended to run above the volatility that subsequently occurs. In the two years to October 29, 2026, the VIX close was higher than the S&P 500 ETF's realized volatility over the following 21 trading days on 420 of 480 days (87.5%). The average VIX over those days was 18.45, against an average forward realized volatility of 14.35. The difference is often described as a premium that option buyers pay for protection.

The exceptions are the dangerous days. On March 25, 2025 the VIX closed at 17.15, below its long-run median. Over the next 21 trading days, which included the early-April sell-off, SPY's realized volatility came to about 52, three times what the index had priced. The VIX then caught up, closing at 52.33 on April 8, its high for the window. Implied volatility is the market's estimate, and events can overtake it.

The VIX since 1990: what the data shows

Cboe's daily file holds 9,305 closes from January 2, 1990 to October 29, 2026. Over that span:

• The median close was 17.56 and the mean 19.42. The VIX closed below 20 on 63.1% of days, above 30 on 7.9% and above 40 on just 2.2%.
• The lowest close was 9.14, on November 3, 2017.
• The highest close was 82.69, on March 16, 2020, during the pandemic crash. Less than four weeks earlier, on February 19, 2020, it had closed at 14.38: a rise of nearly six-fold. Its highest intraday level that month was 85.47, on March 18.
• In the 2008 financial crisis the VIX closed at 80.86 on November 20, 2008, and reached its highest intraday level in the data, 89.53, on October 24, 2008.

Spikes fade faster than they build. After the November 2008 peak the VIX did not close below 30 until May 19, 2009, nor below 20 until December 22, 2009. After March 2020, its first close below 20 came on February 12, 2021.

Intraday and closing figures can tell very different stories. On August 5, 2024 the VIX traded as high as 65.73 during the day but closed at 38.57, which is why this page quotes closes unless it says otherwise.

Pitfalls when reading the VIX

• High is not a timing signal. A high VIX means option buyers expect large moves; it does not say which direction, or when they will stop.
• Low is not safety. The 2017 lows were followed by a sharp spike in February 2018, when the VIX closed at 37.32 on February 5.
• Mean reversion takes time. Over decades the VIX has drifted back toward its median, but after 2008 it stayed above 20 for more than a year.

VIX products are not the VIX

The VIX is a calculated index; there is no way to buy it directly. Exposure comes through VIX futures and options, and through exchange-traded products (ETPs) that hold or track VIX futures. FINRA's investor page on volatility investing stresses that these products generally track VIX futures rather than the index, can diverge significantly from the VIX, especially over longer periods, are generally not designed for buy-and-hold investing, and can lose some or all of their value in a short time. Some are leveraged or inverse, which adds complexity, and some are exchange-traded notes (ETNs), which are unsecured debt of their issuer.

The divergence has a mechanical source. A fund that holds short-dated VIX futures must keep selling contracts as they approach expiration and buying later ones. When later futures are priced above earlier ones, which is common in calm markets, each roll sells low and buys high, and the product's value tends to erode even if the VIX itself goes nowhere. In a spike the relationship can reverse. Read the prospectus before relying on any of these products; this page describes the mechanics, not how to use them.

Volatility measures compared

How Finabase helps

Finabase is a research app; it doesn't trade options or volatility products. It does put the relevant data in one place:

• The VIX symbol page shows the index's quote and an interactive chart, and you can open the full VIX chart for longer ranges.
• The options chain lists calls and puts by expiration with bid, ask, last, volume, open interest and implied volatility for each contract, so you can see the raw material that indexes like the VIX are built from.
• The indices page compares the major market indexes.
• For a backward-looking measure on any stock, add the ATR study to its chart, as in the AAPL chart with ATR (14).

Frequently asked questions

What is a normal level for the VIX?

Based on Cboe's daily data from 1990 to October 2026, the VIX's median close was 17.56, and it closed below 20 on about 63% of days. Readings above 30 occurred on about 8% of days and above 40 on about 2%.

What was the highest VIX ever?

The highest VIX close in Cboe's data is 82.69, on March 16, 2020. The highest intraday reading is 89.53, on October 24, 2008.

What is the difference between historical and implied volatility?

Historical volatility is calculated from how much prices actually moved in the past. Implied volatility is derived from current option prices and reflects how much movement the market expects, plus what traders will pay for protection.

Can you invest in the VIX directly?

No. The VIX is a calculated index. Investors get exposure through VIX futures, options and ETPs that track futures, and FINRA cautions that those products can behave very differently from the index and are generally not designed to be held long term.

Summary

Volatility measures how much prices move. Historical volatility looks back at actual returns; implied volatility reads expectations out of option prices. The Cboe VIX condenses the S&P 500 options market into a 30-day implied-volatility index, built since 2003 from a wide strip of SPX puts and calls. Its history from 1990 to 2026 shows long calm stretches around a median of 17.56, punctuated by violent spikes, with closes of 80.86 in November 2008 and a record 82.69 in March 2020. Implied volatility has usually sat above what followed, but not always, and products linked to the VIX follow its futures, not the index itself.