VIX at 20 means the market expects daily moves of about 1.26%
The “fear index” is an annualized standard deviation taken from S&P 500 option prices. Divide it by the square root of 252 and it becomes a daily move.
- What happened
- The Cboe Volatility Index is a 30-day expected volatility of the S&P 500, implied by SPX option prices and quoted as an annualized percentage. Cboe's own page showed it at 14.87 at the close on September 25, 2026; FRED's copy of the series showed 14.21 for September 22, 2026.
- Why
- An annualized standard deviation converts to a daily one by dividing by the square root of 252 trading days. A VIX of 20 is therefore an expected one-day move of about 1.26%, in either direction, with no view on which.
- The numbers that matter
- 14.87VIX close, September 25, 2026 (Cboe)1.26%One-day move implied by VIX 20 (calculation)5.77%30-day move implied by VIX 20 (calculation)4.2 ptsAverage VIX minus realized volatility, 1990–2018 (Cboe)
- Why it matters
- The number tells you how wide a range option traders are pricing for the 30 days ahead, which is useful for sizing what a normal week can do to a portfolio. It says nothing about direction and is not something you can buy.
- What happens nextas we saw it on 28 Sep 2026
- Cboe recalculates the index roughly four times a minute during trading hours; FRED posts each day's close on the following business day.
Every VIX reading is a daily percentage in disguise: divide by 15.87, the square root of 252 trading days.
| VIX 12 | 0.8% |
|---|---|
| VIX 16 | 1.0% |
| VIX 20 | 1.3% |
| VIX 30 | 1.9% |
| VIX 40 | 2.5% |
| VIX 80 | 5.0% |
The VIX is not a mood. It is a standard deviation with the units left off. Cboe publishes it as an annualized percentage, and the only thing between a reading of 20 and a plain statement about the next trading day is one division: 20 divided by the square root of 252 is 1.26. That is the expected size of a one-day move in the S&P 500, up or down, with no view on which.
What Cboe actually calculates
Cboe's methodology document, version 6.0, last revised February 26, 2026, states that the index is designed to “measure the market's expectation of 30-day forward looking volatility of the U.S. equity market, as conveyed by S&P 500 Index option prices.” The inputs are option prices, not the index itself and not a survey of anyone's feelings.
Cboe takes two option expirations that bracket the 30-day point, using AM-settled SPX and PM-settled weekly SPXW contracts. For each it collects a strip of out-of-the-money options: puts with strikes below the forward level, calls above it, working outward and stopping once two consecutive strikes show no bid. Each mid-price is weighted by the strike gap divided by the strike squared, and the weighted sum is a variance for that expiration.
Cboe describes the last stage as “calculate the 30-day weighted average of σ₁² and σ₂². Then take the square root of that value and multiply by 100.” The square root turns variance into a standard deviation and the factor of 100 turns a decimal into percentage points. That is why the VIX is quoted as 14.87 and not 0.1487.
Two consequences follow. The index is annualized, because option pricing expresses volatility per year. And it is symmetric, built from puts and calls on both sides of the current level: a reading of 20 prices a 20% range, not a 20% fall. Cboe's education post of April 24, 2023 calls the output “a non-directional, annualized expectation for the standard deviation of the S&P 500.” See implied volatility in the glossary.
From a year to a day
Volatility scales with the square root of time. An annual standard deviation becomes a daily one by dividing by the square root of the trading days in a year, by convention 252. Dividing by the square root of 12 gives a 30-day figure.
Inputs: VIX = 20, trading days per year = 252. √252 = 15.8745. Result: 20 ÷ 15.8745 = 1.26%. For the September 25, 2026 close of 14.87: 14.87 ÷ 15.8745 = 0.94%.
Inputs: VIX = 20, months per year = 12. √12 = 3.4641. Result: 20 ÷ 3.4641 = 5.77%. At 14.87: 14.87 ÷ 3.4641 = 4.29%. This is the horizon the index is built for.
Because 16 ÷ 15.8745 = 1.008, dividing a VIX reading by 16 gives the daily move to within about 1%. VIX 20 ÷ 16 = 1.25% against the exact 1.26%. Cboe's April 24, 2023 post uses the same shortcut: “the VIX Index at 16 means an expected +/- 16% annual move for the S&P 500, which would equal a daily range of +/- ~1%.”
| VIX level | Expected one-day move (÷ √252) | Expected 30-day move (÷ √12) |
|---|---|---|
| 12 | 0.76% | 3.46% |
| 14.87 (Sep 25, 2026 close) | 0.94% | 4.29% |
| 16 | 1.01% | 4.62% |
| 20 | 1.26% | 5.77% |
| 30 | 1.89% | 8.66% |
| 40 | 2.52% | 11.55% |
| 82.7 (Mar 16, 2020 close, per Cboe) | 5.21% | 23.87% |
A standard deviation describes a typical move, not a limit. In a normal distribution about 68% of outcomes fall within one standard deviation of the center, and equity returns have fatter tails than that, which is one reason a VIX of 82.7 still understated the day it was set.
Where 14.87 sits
Cboe's VIX product page, retrieved September 28, 2026, showed the index at 14.87 with data as of 8:15 PM on September 25, 2026, down 0.80 points, or 5.11%, on the day. The page gave a 52-week high of 35.30 and a 52-week low of 13.38: in daily terms, 2.22% and 0.84%. FRED's VIXCLS series, which redistributes Cboe's daily closes, showed 14.21 for September 22, 2026, its most recent observation when retrieved (page updated September 23, 2026).
Cboe's own history of the index supplies the extreme. In a note dated September 8, 2025 attributing the index's largest one-day jumps, Cboe records that on March 16, 2020 “the S&P 500 Index declined 12% and tripped exchange circuit breakers” and “the VIX Index increased 24.9 points from 57.8 to 82.7.”
The prior close of 57.8 implied a one-day move of 57.8 ÷ 15.8745 = 3.64%. The S&P 500 fell 12% that day, about 3.3 times the expected move. Even the closing reading of 82.7 implied 5.21%, under half of what had just happened. The index prices a range; it does not cap it.
The site's Market Memory tool (listed on the tools page) does the reverse exercise, ranking a day's S&P 500 move against history; the Silicon Valley Bank autopsy is a worked example of implied and realized volatility parting company.
Implied is usually above realized
The VIX is a price, and prices contain a premium. Someone selling an S&P 500 put takes on the risk of a crash and charges for it, so the index built from option prices sits above what the market subsequently delivers most of the time. Cboe calls the gap the volatility risk premium.
A Cboe post of May 29, 2019 summarizing a white paper by Oleg Bondarenko of the University of Illinois at Chicago states that from 1990 to 2018 “the average implied volatility, as measured by the Cboe Volatility Index (VIX), was 19.3%, while the average realized volatility of the S&P 500 Index was 15.1%. The Volatility Risk Premium (VRP) was a significant difference of 4.2 percentage points.”
19.3 ÷ 15.1 = 1.278, so on Cboe's figures the index overstated subsequent realized volatility by about 28% on average across 1990–2018. A May 2014 Russell Investments paper hosted by Cboe reports the same order of magnitude: implied volatility “exceeded subsequent annualized realized volatility by 28%, on average, since 1990” and did so “more than 80% of the time.”
A reading of 20 is what the market charges for protection against a 20%-a-year world, and the charge includes a margin for the seller. Realized moves have on average come in smaller. That does not make the number wrong; it makes it a price. The gap inverts in a crisis, as the March 16, 2020 arithmetic shows.
The index is not a product
Nobody owns the VIX. It is a calculation refreshed roughly four times a minute from a strip of options that changes as expirations roll. What trades are VIX futures, introduced by Cboe in 2004, and the exchange-traded products built on them. A future settles to the index level on its expiration date, so a one-month future is a bet on where the VIX stands in a month.
The future and the spot index can therefore differ by several points on any day. When later months sit above spot the curve is in contango, and a product that holds those futures and rolls them forward pays the difference at each roll. That cost compounds, which is why a VIX-linked product and the VIX itself can move very differently.
The structure of the fund matters more than its name. And as the volatility is not risk entry explains, a high VIX describes the width of the expected range, not by itself a household's odds of losing money over a horizon that matters.
What it means for your money
Take a VIX reading, divide by 16, and you have the size of a normal day in percentage terms. Divide by 3.46 and you have a normal month.
At 14.87: a one-standard-deviation day is 0.94% of $100,000, or $940; a one-standard-deviation 30-day move is 4.29%, or $4,290. At 30: the daily figure is 1.89%, or $1,890, and the 30-day figure is 8.66%, or $8,660. These are typical sizes, not limits, and they apply in both directions.
- A drawdown that would force you to sell is the number to compare against the 30-day figure, not the daily one.
- The premium documented above means the range the VIX implies has, on average since 1990, been wider than the range that arrived.
- The position-sizing entry and the loss-recovery tool turn a percentage move into the gain needed to get back to even; the 10-year Treasury at 5% and the Russell record while the S&P slipped are the September 2026 market pieces this reading sits alongside.
Sources
- Cboe Volatility Index Methodology, version 6.0, last revised February 26, 2026Cboe Global Indices · Sep 28, 2026 · Primary source
- VIX Volatility Products — VIX Index quote, 52-week range, data as of 8:15 PM 9/25/2026Cboe Global Markets · Sep 28, 2026 · Primary source
- What the VIX and VIX1D Indices Attempt to Measure and How They Differ (Spencer Doar, April 24, 2023)Cboe Global Markets · Sep 28, 2026 · Primary source
- VIX Index Attribution of Notable Tail Events (September 8, 2025)Cboe Global Markets · Sep 28, 2026 · Primary source
- White Paper Shows Volatility Risk Premium Facilitated Higher Risk-Adjusted Returns for PUT Index (May 29, 2019), summarising Oleg Bondarenko, Historical Performance of Put-Writing StrategiesCboe Global Markets · Sep 28, 2026 · Primary source
- Strategy Spotlight: Considerations in Volatility Trading (Scott Maidel, May 2014), hosted by CboeRussell Investments via Cboe · Sep 28, 2026 · Primary source
- CBOE Volatility Index: VIX (VIXCLS), observation of September 15, 2026Cboe Global Markets via FRED · Sep 15, 2026 · Primary source
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