How does VIX expiration and settlement work?

Why it expires on a Wednesday

The VIX index measures the 30-day implied volatility of the S&P 500, calculated from a strip of SPX option prices. For a VIX futures contract to settle to a clean 30-day measure, its settlement needs to use SPX options that expire exactly 30 days later. So the standard monthly VIX expiration is set on the Wednesday that falls 30 days before the third Friday of the following month, the date standard SPX options expire.

If holidays interfere, the date shifts. The general rule to remember is that VIX expiration is a Wednesday, typically in the middle of the month, and not the third Friday like most equity options. Weekly VIX futures and options also exist, with their own Wednesday expiries.

Trading in the expiring contracts usually stops the day before, on Tuesday, so final settlement is determined Wednesday morning, after trading in those contracts has ended.

How the settlement value is calculated

On the morning of expiration, a special opening quotation is calculated using the VIX formula, but instead of the continuously updating quotes used during the day, it uses the actual opening prices of the relevant SPX options. This value is published under its own ticker, commonly referred to as VRO.

Because it depends on how hundreds of SPX option series open, often including far out-of-the-money puts with thin markets, the settlement can land some distance from the prior day's VIX close or from where VIX indicates shortly after the open. Market participants trade SPX options at the open specifically to manage their VIX settlement exposure, which adds to opening activity on those mornings.

The result is a single settlement number that determines the cash payout of every expiring VIX future and option. Like SPX, VIX derivatives are cash-settled; there is nothing to deliver.

Why the settlement can surprise

Spot VIX during the trading day is calculated from the midpoints of SPX option quotes. The settlement uses actual opening trade prices instead, and in thinly traded far out-of-the-money strikes those opening prices can differ from the prior midpoints. Small differences across many strikes add up to a settlement that can sit noticeably above or below the VIX level traders had in mind.

There is also an overnight gap. Settlement is set at Wednesday's open, after the expiring contracts have stopped trading on Tuesday. Any news between the two, and any move in S&P 500 futures overnight, feeds into the opening SPX option prices and therefore into the settlement, with no opportunity to adjust the expiring position.

VIX options are priced off futures, not spot

This is the most common misunderstanding about VIX options. They settle to the same value as the VIX future of the same expiration, so their prices are driven by that future, not by the spot VIX index you see quoted on screens. When VIX futures are in contango, a VIX call can look expensive relative to spot VIX because it is priced against a higher futures level.

For the same reason, a rise in spot VIX does not translate one for one into VIX option gains. Longer-dated VIX futures typically move less than spot during a spike, so options on those futures move less too. The option a trader holds tracks its own future.

As expiration approaches, the front future converges toward where settlement is expected to land, and the distinction narrows. Far from expiry, it is large.

Why VIX expiration can matter to SPX

Because settlement is drawn from SPX option opening prices, VIX expiration mornings bring concentrated trading in SPX options, particularly the out-of-the-money puts that dominate the VIX calculation. That trading is mostly hedging and positioning around settlement rather than a view on the index.

Expiring VIX positions also remove hedges. Large holders of VIX calls, used as protection on equity portfolios, have offsetting exposures in SPX or VIX futures held by dealers. When those contracts expire, the related hedges are adjusted, which can contribute to volatility-market flows around the date, though the size and direction depend on positioning that is not public.

None of this means VIX expiration moves the stock market in a predictable way. It is a known date with concentrated activity in a specific set of SPX options, which is worth knowing when reading unusual volume or price action at the open on those Wednesdays.