How to read the VIX: definition, levels, and spikes
- The VIX is an index calculated from S&P 500 option prices.
- The period it covers is 30 days, and the figure is an annualized volatility.
- It is a different number from a percentage change in share prices or the price of cash equities.
Section highlights (6)
- The VIX is calculated from S&P 500 options.
- The period is 30 days; the figure is shown annualized.
- A VIX value is a level of volatility, not a percentage change in share prices.
- The VIX, equity indices and perpetual-futures reference values differ in subject and unit.
- Solid and dashed lines separate time periods, and both show reference values.
- StockTicker24 has no VIX card; the VIX-named contract in the provider's data is marked as delisted and is not shown on the board. The 42 saved records from 8 August to 22 September 2026 contain 0 mid prices, so no VIX value or percentage change is calculated.
Contents
The VIX is Cboe's volatility index. Volatility is a measure of the size of price movement.
This article sets out what the VIX is calculated from, the period it covers, and its unit. It does not attach a market-state or trading label to any level.
What the VIX is calculated from
The input is S&P 500 options
It is calculated by Cboe, the Chicago Board Options Exchange. The basis is S&P 500 index (SPX) option prices.
An option is a contract giving the right to buy or sell on set terms. The input to the VIX is option prices, not the cash prices of the shares themselves.
The VIX is calculated from S&P 500 options.
Quotes and time to expiry
Cboe's description of the calculation uses the midpoint of bid and ask quotes on SPX options with 23 to 37 days to expiry. From these, a figure covering the next 30 days is calculated.
| Item | Definition |
|---|---|
| Input | Midpoint of SPX option bid and ask quotes |
| Time to expiry of the input options | 23 to 37 days |
| Period the index covers | 30 days |
| Display unit | Annualized volatility (%) |
The unit and the level of the figure
30 days and annualized
The 30 days is the period the calculation covers. Annualized is the unit the figure is shown in. It does not mean the period is one year.
The VIX is an index of implied volatility. That is volatility calculated from option prices. Realised volatility is calculated from past share-price changes, so its input is different.
The period is 30 days; the figure is shown annualized.
What values such as 20 and 30 mean
A VIX value of 20 is a unit of 20% annualized volatility, and 30 is 30% annualized volatility. It is not a record that the S&P 500 price changed by 20% or 30%.
| VIX value | Written as annualized volatility |
|---|---|
| 20 | 20% |
| 30 | 30% |
This table explains the unit. It does not divide trading or market conditions at 20 or 30.
A VIX value is a level of volatility, not a percentage change in share prices.
The level versus a percentage change
The level of the VIX, the change in the VIX from its previous value, and the percentage change in the S&P 500 are separate numbers. The level of the VIX alone carries no sign for a rise or fall in share prices.
A number being compared needs a subject and a unit. For the VIX that is the index level, for the S&P 500 the level of the equity index, and for a change over a period its start and end points.
Differences from StockTicker24's reference values
What each number covers
StockTicker24 does not carry the VIX itself. The figures for equity indices and other instruments on the board are reference values based on perpetual-futures prices from offshore derivatives venues.
A perpetual future is a contract with no settlement date. Its price, cash share prices, the official equity index and the VIX are not the same values.
| Number | What is calculated and shown |
|---|---|
| VIX | Volatility calculated from S&P 500 options |
| S&P 500 index | Equity index calculated from constituent share prices |
| This site's reference values | Perpetual-futures prices |
The VIX, equity indices and perpetual-futures reference values differ in subject and unit.
How solid and dashed lines are defined
On price-discovery cards, a solid line marks the related cash market's set session hours and a dashed line the rest. Reference-value cards draw the whole line solid.
Both line styles show the same perpetual-futures reference series. Neither is a VIX line. The price categories are also described in the S&P 500 outside U.S. cash hours and on weekends.
Solid and dashed lines separate time periods, and both show reference values.
From this site's records
StockTicker24 has no VIX card; the VIX-named contract in the provider's data is marked as delisted and is not shown on the board. The 42 saved records from 8 August to 22 September 2026 contain 0 mid prices, so no VIX value or percentage change is calculated.
Common questions
What is the VIX calculated from?
Quotes on S&P 500 options. It is calculated by Cboe, the Chicago Board Options Exchange.
Do "30 days" and "annualized" mean the same thing?
The 30 days is the period covered. Annualized is the unit the figure is converted to.
Are 20 and 30 boundaries between categories?
In this article they are example values showing the unit of annualized volatility. They are not used to classify market conditions.
Can I see the VIX on StockTicker24?
StockTicker24 does not carry the VIX itself. The board shows perpetual-futures reference values.
Summary
- The VIX is a volatility index calculated from S&P 500 options.
- The period it covers is 30 days, and the figure is shown annualized.
- It is kept separate from percentage changes in share prices, equity-index levels and perpetual-futures prices.
- StockTicker24's solid and dashed lines separate the time periods of the reference values.
This article is for information only and is not investment advice.
Change log: 29 Sep 2026. Added “From this site's records” and replaced the level-band reading with the definition of the period and unit.
Source: Cboe / Published: / Last updated: / Perpetual-futures prices are reference values.