What Is the VIX?
VIX is an option-derived measure of expected S&P 500 volatility over a constant 30-day horizon. It is not a crash probability.
Definition and scale
Cboe derives VIX from SPX option quotes and expresses its constant 30-day volatility measure on an annualised scale. It is forward-looking and option-derived; historical realised volatility is a calculation from already observed returns.
Worked interpretation
A hypothetical VIX reading of 20 represents 20% annualised volatility, not a forecast of a 20% move next month. A simple horizon conversion is 20% × √(30/365) ≈ 5.73% for 30 calendar days. This is an illustrative scale conversion, not a literal probability guarantee or Cboe trading recommendation.
That scale also carries no direction. A larger volatility estimate can involve upward or downward movement. ‘20’ does not mean a 20% probability of a crash.
Spot VIX versus tradable products
The index itself is not a share you can buy. Futures, options and exchange-traded products linked to volatility have their own pricing and exposure. Their returns need not equal the change in spot VIX; maturity and roll effects matter.
Use the right comparison
For a research comparison, identify timestamp, horizon and whether each input comes from option prices or historical returns. Avoid treating a qualitative ‘fear gauge’ label as a numeric forecast.
Aiovel’s S&P 500 model estimates use historical price data and an ATR proxy, rather than VIX or SPX option quotes.
Sources and checks
Definitions checked against the references below on September 17, 2026. Worked examples are illustrative unless explicitly dated. These references do not validate Aiovel forecasts.
Explore the dated public sample and check its source timestamp before using it.
Explore the probability cone →Quick answers
Does VIX predict a market fall?
No. It measures option-implied volatility, rather than direction or a crash probability.
Is VIX 20 a 20% monthly move?
No. The figure is annualised even though its constant measurement horizon is 30 days.