# Change in Open Interest: How to Read Options OI Change Source: SquawkFlow URL: https://squawkflow.com/learn/change-in-open-interest-options Category: Options Basics Published: 2026-10-02 Type: Explainer > What a change in open interest in options measures, when the number is published, what volume can and cannot prove, and why it carries no direction. --- ## What change in open interest measures Open interest is the count of option contracts that exist right now: opened, and not yet closed, exercised, assigned or expired. The change in open interest is simply today's count minus yesterday's count for the same contract, meaning the same underlying, strike, expiration and type. If an SPX call had 4,000 contracts open at the last settlement and 6,500 open at this one, the change is +2,500. That sounds trivial, and the basic version is covered in our [guide to options open interest](/learn/options-open-interest-explained). The interesting part is what the number can and cannot tell you. Most pages that rank for this query stop at "rising open interest means new money" and then borrow a price and open interest table from the futures world. That table skips three things that matter in options: when the number is computed, how little a single day's change actually pins down, and the fact that every new option contract has a buyer and a writer. ## When the number is published Open interest is not a live quote. The Options Clearing Corporation computes it once per day. As Market Chameleon's Dmitry Pargamanik put it on an [Interactive Brokers podcast](https://www.interactivebrokers.com/campus/podcasts/ibkr-podcasts/what-is-option-open-interest-and-how-to-analyze/), the calculation is "done overnight by the Options Clearing Corporation based on end-of-day settled trades," it "takes into consideration any type of corporate actions, exercises, or expirations," and after a reconciliation process the OCC makes "the new open interest available the following day." The [Options Playbook](https://optionsplaybook.com/options-introduction/open-interest) describes the same cadence: the figure is "officially posted by The OCC the morning after any given trading session." Two practical consequences follow. - **The change is always about yesterday.** The open interest you see during Thursday's session describes positions as of Wednesday's close. Whatever happened on Thursday shows up in Friday morning's number. - **Volume and open interest change come from different clocks.** Volume accumulates during the session; the open interest change that explains it arrives the next morning. Pairing today's volume with today's displayed open interest compares two different days. ## The arithmetic: what volume can and cannot prove Every contract that trades has two sides, and each side is either opening or closing. The [Options Industry Council](https://www.optionseducation.org/news/open-interest-why-it-matters) walks through the three cases with ten contracts: buy to open against sell to open adds 10; sell to close against buy to close removes 10; one side closing while a new trader opens leaves the count unchanged. Our [volume vs open interest guide](/learn/options-volume-vs-open-interest) covers the same mechanics. Put those three cases together and you get a bound that most guides never state. Ignoring exercise and expiration for a moment, call the contracts that were opened on both sides O, closed on both sides C, and simply transferred T. Then: - the day's volume is O + C + T - the change in open interest is O minus C So a change in open interest sets a floor on new positions, not a total. Take a contract that traded 12,000 times while its open interest rose by 3,000. At least 3,000 contracts were opened on both sides. At most 7,500 were, which happens if the other 9,000 contracts of volume were 4,500 opened and 4,500 closed. Anywhere from 3,000 to 7,500 new contracts is consistent with the same two numbers. The bound runs the other way on a decline. If open interest fell by 3,000 on the same 12,000 contracts, at least 3,000 were closed on both sides, and up to 4,500 contracts could still have been fresh openings hidden underneath the closing. This is why a large change on small volume is the more informative reading. If a contract traded 3,200 times and open interest rose 3,000, nearly all of the volume must have been opening trades. On 40,000 contracts of volume the same +3,000 is consistent with a much more mixed day. ## Changes that have nothing to do with trading The podcast quote above names the three ways open interest moves without anyone trading to close. 1. **Exercise and assignment.** The Options Industry Council notes that exercised contracts that result in assignment are "closed" and eliminated from open interest. A deep in-the-money call exercised early, for example ahead of a dividend, disappears from the count with no closing trade on the tape. 2. **Expiration.** Expiring contracts leave the count entirely. If you add up a ticker's total open interest the day before and the day after a large monthly expiration, the aggregate change is dominated by contracts that simply ceased to exist. A ticker-level "open interest fell 30%" headline the morning after expiration usually means nothing beyond the calendar. Compare only contracts that were alive on both dates. 3. **Corporate actions.** Splits, special dividends and mergers can adjust contract terms. The adjusted series can show changes that reflect the reorganization, not anyone's view. ## Why the futures table does not transfer cleanly The familiar interpretation table comes from futures. CME Group's [open interest lesson](https://www.cmegroup.com/education/courses/introduction-to-futures/open-interest.html) teaches that increasing open interest is typically a confirmation of the trend, and that rising prices with rising open interest is a bullish signal. Several options guides repeat this table with "calls" or "puts" pasted in. In a futures market that reading at least refers to far fewer contracts per underlying. An options chain has hundreds of contracts, and each new one has a writer as well as a holder. An open interest build at a call strike is equally consistent with: - speculators buying calls from market makers, - shareholders selling covered calls against stock they already own, - one leg of a spread whose other leg built at a neighboring strike, or - a fund rolling a hedge from one expiration to the next. The first is the bullish story. The second is a holder capping upside for income. The third and fourth carry little directional information on their own. The open interest number is identical in all four cases. To tell them apart you need the side of the trade, the option's price change, and the matching legs, which is the work described in [how to tell if an option was bought or sold](/learn/how-to-tell-if-an-option-was-bought-or-sold). ## What the research says Changes in open interest do carry information on average, which is part of why traders watch them. Fodor, Krieger and Doran, in [Financial Markets and Portfolio Management (2011)](https://doi.org/10.1007/s11408-011-0164-z), report that "large increases in call open interest are followed by significantly increased equity returns," that put open interest increases precede weaker returns but less robustly, and that the change in the call to put open interest ratio has predictive power for the following week. At the index level, Seo, Byun and Kim in the [Journal of Futures Markets (2020)](https://ideas.repec.org/a/wly/jfutmk/v40y2020i6p989-1010.html) find that growth in out-of-the-money index call open interest is significantly related to future stock market returns, and they model it through hedgers who adjust option use to their expectations. Two caveats keep this honest. Both are statistical results over large samples, not rules for any single strike on any single morning. And both measure aggregates such as total call or put open interest over a period, which is a very different object from one contract that built 2,000 overnight. ## A reading checklist When you look at a change in open interest, these steps turn the number into something you can reason about. 1. **Check the dates.** Confirm which two settlements are being compared, and that they are consecutive sessions. 2. **Drop what expired.** Compare only contracts that were alive on both dates, so expiration roll-off does not pose as positioning. 3. **Set it against volume.** Use the floor and ceiling above. A change close to the day's volume says the activity was mostly opening; a small change on huge volume says almost nothing. 4. **Look for the pair.** Equal builds at two strikes in the same expiration usually mean a spread, which reads as one position. 5. **Find the side.** Open interest has no direction. Bring in trade side and the option's price move before calling a build bullish or bearish. 6. **Ask what it does to hedging.** New open interest changes dealer exposure only if dealers took the other side. That assumption is the core of every [gamma exposure](/learn/what-is-gamma-exposure-gex) model, and it is worth stating out loud whenever a build is used to explain a level. ## Seeing it on SquawkFlow The free [overnight open interest change](/oi-change) page applies the first two steps for SPX. It compares two consecutive Cboe-reported settlements, drops contracts that expired on or before the newer settlement, and lists the largest builds and drops by strike along with the net change across calls and puts. It is refreshed once per session before the open. It is not volume and not order flow, and each row is a strike and expiration, not a trade. Settlement open interest also feeds the dealer gamma estimates on [/gex](/gex), so a large overnight build at a strike is the first place to look when a level moves. *Educational content, not financial advice. See our [risk disclosure](/risk-disclosure).* --- ## Citation Source: SquawkFlow, https://squawkflow.com/learn/change-in-open-interest-options Retrieved: 2026-10-08 16:19 ET Attribution: cite the page URL rather than a copied number. Levels are recomputed every session, so a number without its date is wrong within a day. SquawkFlow publishes market-structure data and education. Nothing here is investment advice, a price target or a recommendation, and we have no order execution.