The chart below graphically represents the calculation for the Cboe’s VIX® with near-real-time (20-minute delayed) data, The actual VIX is located on the black dotted line in the left-center of the graph. Click here for a larger snapshot for 12-Nov-2014. The VIX now uses interpolation between two VIX style calculations (VIN and VIF) on SPX options series that are a week apart—bracketing the 30-day target horizon of the VIX.
There are two somewhat parallel markets associated with general USA market volatility: the S&P 500 (SPX) options market and the VIX Futures market. SPX option prices are used to calculate the Cboe’s family of volatility indexes, with the VIX® being the flagship. VIX futures are priced directly in expected volatility for contracts expiring up to 9 months out. The nearest VIX Future synchronizes with the VIX once a month—on its expiration date.