Volatility

VIX Index

By Ryan Silk & Lawrence Polatchek · Reviewed April 2026 · Options Trading Glossary

Market's 30-day forward volatility expectation

What is VIX Index?

VIX Index The CBOE Volatility Index, often called the 'fear gauge,' measures the market's expectation of 30-day forward volatility derived from S&P 500 index option prices. VIX is calculated from a wide strip of SPX options and represents the implied volatility of a hypothetical 30-day at-the-money SPX option. VIX typically rises during market declines and falls during rallies.

Complete Definition

The CBOE Volatility Index, often called the 'fear gauge,' measures the market's expectation of 30-day forward volatility derived from S&P 500 index option prices. VIX is calculated from a wide strip of SPX options and represents the implied volatility of a hypothetical 30-day at-the-money SPX option. VIX typically rises during market declines and falls during rallies.

Example

VIX at 15 implies the market expects the S&P 500 to move about 4.3% over the next 30 days (15/sqrt(12)).

Related Terms

Implied Volatility Vix Futures Volatility Of Volatility Cboe

Written by

ApexVol Research Team

Quantitative options research

All calculations use live ORATS institutional data — the same source used by professional volatility desks.

Technical reviewer

Ryan Silk, ApexVol Founder

Reviewed for technical accuracy

10+ years trading options. Built ApexVol's pricing engine, Greeks model, and IV-rank methodology.

This guide is updated as market conditions and ORATS data change. Last revised 2026-05-12. How we research →

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