VIX1D Closed at 13.09 and VIX9D at 18.13: Why the Horizon Matters More Than the Gap

Different horizons, different readings

Four Cboe volatility gauges finished Monday, 27 July 2026, with four different readings. VIX1D closed at 13.09, VIX9D at 18.13, VIX at 18.67 and VIX3M at 20.20. It was the latest completed U.S. session when this article was prepared at 07:00 AEST on Tuesday, 28 July.

The session changes were equally uneven. VIX1D fell 2.34 volatility points, VIX9D rose 0.51, VIX rose 0.09 and VIX3M fell 0.31. A single label such as "volatility rose" or "volatility fell" would discard most of the information.

The curve showed that horizon mattered. It did not predict market direction, identify a trade or assign a precise amount of volatility to the Federal Reserve meeting. Each index looked through a different window of time, and the gaps between annualised readings require variance arithmetic before they can support a stronger claim.

Four cameras, one options market

Imagine four cameras pointed at the same calendar. The first frames the next trading day. The second captures nine days. The third sees 30 days, and the fourth covers roughly three months. An event outside the first frame can sit inside all three longer views.

Cboe builds each volatility index from SPX option prices, but the target horizons and eligible option strips differ.

VIX1D uses SPX options expiring on the current and next trading day, with weights that shift through the session. Cboe calculates it with business minutes and business years. VIX9D applies the VIX method to a constant nine-day horizon. VIX is the familiar constant 30-day measure, and VIX3M targets 93 days.

Each value is an annualised, non-directional volatility reading. Contract prices, probabilities and expected index direction require separate evidence.

The 5.04-point gap needs a variance calculation

VIX9D closed 5.04 points above VIX1D. Subtracting the two levels describes the curve's shape. Total variance requires squaring each annualised level and weighting it by time.

The basic conversion is:

Total variance = annualised volatility squared x time

A forward segment can then be estimated by subtracting the shorter horizon's total variance from the longer horizon's total variance. The cleanest illustration from the 27 July curve uses VIX9D and VIX because both follow the VIX constant-maturity framework without importing VIX1D's different business-time clock.

The following calculation uses a common 365-day year and treats the displayed closes as exact horizon inputs:

The 0.54-point gap between VIX9D and VIX therefore does not become 0.54 points of "later volatility". Under the stated model, the residual 21-day segment carries an annualised volatility of about 18.90%.

The observed Cboe closes are inputs to a simplified model. Cboe did not publish the 18.90% forward figure. Its index calculations use option mid-quotes, selected strikes, risk-free rates, near- and next-term expirations and minute-based time weights. The model also says nothing about the path of the S&P 500 or the size of any one day's move.

Direct forward-variance arithmetic between VIX1D and VIX9D needs further care because VIX1D uses business time while the longer VIX-family calculations use their own constant-maturity conventions. The 5.04-point gap remains a curve-shape observation; a clean event-volatility estimate requires aligned methods and horizons.

Scheduled events sit inside the longer frame

The timing gives the curve an immediate research use. The Federal Open Market Committee's two-day meeting begins on Tuesday, 28 July. The policy statement is scheduled for 2:00 p.m. Eastern time on Wednesday, 29 July, followed by the press conference at 2:30 p.m. The Bureau of Economic Analysis schedules advance second-quarter GDP and June Personal Income and Outlays for 8:30 a.m. on Thursday, 30 July.

At the end of the 27 July session, Cboe's VIX1D calculation had converged to the next-day SPX option strip. Its immediate frame ended before the scheduled policy decision. The nine-day, 30-day and 93-day gauges all extended across the Fed and BEA releases.

Interpretation begins here, after the facts. The upward sequence from 13.09 to 18.13 to 18.67 to 20.20 is consistent with more annualised uncertainty across the longer frames than across the next trading day. The public index levels cannot tell how much of that difference belongs to the Fed, GDP, PCE, other news, downside skew or ordinary uncertainty accumulated over more time.

The four headline indices provide context. Event attribution would need contemporaneous option quotes around the relevant expirations, a documented variance method and a comparison that holds strike selection, quote time and settlement conventions constant.

From index observation to executable contract

Cboe calculates and disseminates the VIX indices, but the spot indices themselves cannot be bought or sold. VIX futures and VIX options are separate instruments with their own expirations, prices and settlement mechanics. SPX options provide another route to volatility exposure, with different strike, liquidity, spread and payoff considerations.

That distinction matters when a curve observation becomes a portfolio question. A trader can correctly identify a steep section of the volatility curve and still choose an instrument whose price, carry, spread or settlement does not behave like the index comparison.

OMP's implied-volatility lesson explains why volatility describes magnitude rather than direction. The options-Greeks guide shows how vega interacts with delta, gamma and theta, while the contract-comparison framework keeps expiration, liquidity and payoff terms beside the volatility reading.

A disciplined term-structure review

A useful review has four steps:

1. Choose the horizon. Match the index window to the date range in the research question.
2. Convert volatility to variance. Square each annualised level and multiply by time before comparing or subtracting horizons.
3. Label fact and interpretation. Record the observed index values separately from any event explanation or forward calculation.
4. Check the instrument. Use live prices, spreads, liquidity, settlement terms and Greeks for the contract that could create the exposure.

The third step prevents a familiar analytical error. A scheduled event can explain why a curve shape deserves attention, but the event calendar alone does not prove what caused the prices.

Sources, limitations and risk

The 27 July closes and changes came from Cboe's official delayed quote records for VIX1D, VIX9D, VIX and VIX3M. Cboe's VIX term-structure page and selected SPX volatility-index methodology define the longer target horizons. Cboe's VIX1D explainer describes its one-day weighting and business-time convention.

Event dates and times came from the Federal Reserve's July 2026 calendar and the BEA release schedule. Schedules can change and should be rechecked if publication moves beyond 28 July.

The forward-volatility example assumes a common 365-day clock and treats the two index closes as exact constant-horizon inputs. It omits quote dispersion, filtering, rates, jumps, skew, trading costs and the details of the constituent option strips. Options can lose substantial value, liquidity can deteriorate and modelled relationships can fail in fast markets.

Options Matrix Pro publishes this article and has a commercial interest in its research platform. The internal links are first-party educational pages. This material is general education, not personal financial advice or a recommendation to buy, sell or hold any security, future or option. Options and volatility products involve risk and are not suitable for every investor.

The decision rule

Choose the clock before reading the level. Use a one-day index for a one-day question and a longer index for a longer question. Convert annualised volatility to total variance before comparing horizons, and require contract-level quotes before turning a curve observation into an execution decision.