Monthly options expiration (OPEX)
OPEX is market shorthand for the monthly options expiration, the day standard monthly equity and index options expire, normally the third Friday of the month. Quarterly OPEX in March, June, September and December coincides with the expiry of equity index futures, and the term is also used loosely for any large expiry.
Senzoukria · Glossary · Updated September 2026
At a glance
- Standard monthly expiry
- Third Friday of the month (earlier if that day is a holiday)
- Quarterly OPEX
- March, June, September, December, alongside index futures expiry
- SPX monthly series
- AM-settled on a special opening quotation that Friday
What expires
Standard monthly options on US stocks, ETFs and indices expire on the third Friday of each month. For SPX, the standard monthly series stops trading on the preceding business day and settles on a special opening quotation computed from the index components' opening prices that Friday, while the SPXW series expiring the same day settles on the close. ETF options such as SPY and QQQ expire at the close and settle by delivery of shares. Weekly and daily expirations now exist on the major index products, so the monthly expiry is one of many, but it usually carries the largest open interest of its month.
Quarterly OPEX
In March, June, September and December, the monthly options expiry falls on the same day as the expiry of quarterly equity index futures such as ES and NQ, which settle to a special opening quotation of their index. Traders often call this day triple or quadruple witching, after the several kinds of contracts that expire together. The combination of settlements and rolls makes volume on those days unusually heavy.
What changes around OPEX
- Before: charm grows on the large expiring series, and gamma concentrates at the strikes nearest spot as expiry approaches.
- At expiry: the expiring series' gamma, vanna and charm disappear from every exposure model at once.
- After: exposure totals are recomputed on the remaining expiries, so levels such as the flip or the walls can jump without any trade having occurred.
- Narratives about post-OPEX weakness or pre-OPEX drift rest on dealer positioning assumptions; they are hypotheses to test, not rules.
In Senzoukria
The GEX module sums every expiry in the window the provider returns and reports that window in the Calculation assumptions panel as the expiry scope. On a day when the nearest expiry is today, the panel lets you include, exclude or isolate 0DTE and shows how far the zero gamma, call wall and put wall move between those variants; on other days the setting is locked, because the nearest expiry is not a same-day expiry. Comparing the levels before and after an OPEX in the Levels history page shows how much of a wall belonged to the expiring series.
Related
In the same section
- Pin risk
- Multi-leg trade
- Monte Carlo simulation
- Naked POC
- Moneyness
- NBBO
- Momentum ignition
- Negative gamma regime
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Frequently asked questions
- Is OPEX always on the third Friday?
- Standard monthly options expire on the third Friday unless it is an exchange holiday, in which case the expiration moves earlier. VIX options follow a different schedule, usually expiring on a Wednesday, and weekly and daily options expire on other days.
- Why do gamma levels jump the Monday after OPEX?
- Because the expired series no longer exist. Their open interest leaves the calculation, and the remaining expiries may place their walls and zero crossing elsewhere. Nothing in the market has to happen for the levels to move.