OPEX Explained: Monthly Options Expiration and the Third-Friday Calendar
· 6 min read
OPEX is short for options expiration. Standard monthly options expire on the third Friday of the month, or on the trading day before if that Friday is an exchange holiday, and that day is called monthly OPEX. If you search for the OPEX date, the answer is simply the third Friday of the month in question. Everything else in this article is about what that day means and how to think about it.
The OPEX calendar for late 2026
The next three monthly OPEX dates are October 16, November 20 and December 18, 2026. Each one is the third Friday of its month. Confirm the exact expiration of a specific contract in your broker’s options chain or the contract specifications.
Four of the twelve monthly dates carry an extra label. The third Friday of March, June, September and December is the quarterly version, often called quadruple witching, because stock options, index options and futures contracts expire together. December 18, 2026 is the next one. Traders pay particular attention to those days because more types of contracts reach the end of their life at once.
Monthly, weekly and daily expirations
Monthly options are the original and most familiar schedule. They are the standard contracts that expire on the third Friday, and they are the reason that day has a name of its own.
Weekly options expire every Friday, so a weekly contract can end on the same day as a monthly one or on any other Friday of the month. Some products also list contracts that expire on other weekdays, and a few popular products offer a contract for every trading day, which is where the term 0DTE comes from. Which products have which schedule varies, so check your broker’s rules and the contract specifications before assuming anything.
Expiration is not a once-a-month event, because contracts end most weeks.
Why traders watch monthly OPEX
On monthly OPEX a large number of contracts reach the end of their life in one session, and that is the reason traders watch it. Holders have to decide whether to close, exercise or let a contract lapse, and sellers have to decide whether to buy back, roll or accept assignment. Many of those decisions land on the same day.
Two effects are commonly discussed. One is pinning, the idea that a stock or index can drift toward a strike where a lot of open contracts are concentrated and linger near it into the close. The other is heavier trading volume as positions are closed or rolled. Both are commonly discussed, neither is certain, and some expiration days pass with nothing unusual at all. Treat them as things you may see, not things you can count on.
What OPEX means for holders
If you hold an option you bought, the clock is the main concern. Time decay works against the buyer, and it matters more as expiration gets close, because the time value left in the contract shrinks toward zero. A contract that is slightly out of the money on expiration morning can lose its remaining value quickly if the underlying does not move.
Holders also face a decision about what happens at the end. A contract that finishes in the money may be exercised or settled according to the product’s rules, and that can mean owning or owing shares you did not plan for. Whether you intend to sell the contract before the close, or hold through it, is a decision that works better when it is made in advance.
What OPEX means for sellers
If you sold an option, expiration week is when assignment risk is most relevant. A short contract that finishes in the money can be assigned, which means you may be required to buy or sell shares at the strike price.
Sellers also face the rolling question, which is whether to close the current position and open a similar one with a later expiration. That choice is usually better made earlier in the week, while there is still time and liquidity, than in the final hour when spreads can be wider and prices move fast. Trading involves risk of loss, and short options can lose more than the premium collected.
Your contract matters more than the headline
A calendar headline that says OPEX is this Friday describes the market in general. Your position has its own expiration date, and that date is the one that matters to your account. A contract expiring in three weeks is not affected by the day in the same way as one expiring this afternoon, even if both belong to the same underlying.
If none of your contracts expire on a given OPEX day, that day may deserve little more than a glance.
A calm way to plan the week
Start by deciding before the day. Write down, ahead of time, what you will do with each open position if the price is above, near or below your strike. A plan made on Monday is easier to follow than a plan improvised at 3:45 on Friday.
Consider sizing smaller during expiration week. Price can move sharply or sit still, and either can surprise you, so a smaller position leaves room for being wrong. Rolling decisions are usually cleaner when made earlier in the week than when left to the last session.
Avoid opening new short-dated contracts that you cannot manage. If you will be away from your screen on Friday afternoon, a contract that expires that day is difficult to watch. Choosing a later expiration, or staying out, is a legitimate decision.
Illustrative hypothetical, not a real trade or a recommendation: suppose you own a call with a strike of 100 that expires on a monthly OPEX Friday, and the stock is near 100 on Wednesday. A reasonable plan written that morning might be to close the position on Thursday rather than hold through the close, so that exercise and settlement questions never arise. The numbers are round and chosen only to show the sequence of planning.
Common mistakes around OPEX
The first mistake is assuming OPEX day always moves the market. Sometimes the session is busy, and sometimes it looks like any other Friday. Building a position around an expected move that may not arrive turns a calendar fact into a prediction.
The second mistake is ignoring that weeklies also expire every Friday. A trader who only marks the third Friday on a calendar can forget that a weekly contract in the account expires a week earlier, or a week later, than the monthly one. Check each contract individually.
Summary
OPEX means options expiration, and monthly OPEX falls on the third Friday of the month: October 16, November 20 and December 18, 2026, with December 18 also being a quarterly date. Traders watch it because many contracts end together, and effects like pinning and heavier volume are commonly discussed but not certain. Your own contract’s expiration is what matters most, so decide before the day, size smaller and avoid short-dated positions you cannot manage. Copied trades can lose money, and trading involves risk of loss.
Curious how mirroring works on a real account? The 7-day free trial connects your account so you can check the fills yourself.
Disclosure: that’s an affiliate link — I may earn a commission if you sign up for a paid plan, at no extra cost to you. There’s a free trial if you want to look around first.
Related reading