--- title: "What are open interest, change in OI and cumulative OI?" description: "Open interest is the number of contracts still open at the end of a session, which NSE's files count in units, so one lot of 65 units is one contract." source_url: "https://www.rupeecase.com/learn/questions/what-is-open-interest" --- Open interest is heaviest at a few round strikes on this chain Calls and puts together, open interest in units at each strike step around the at the money strike, 30 Jun 2026 expiry, 10 Jun 2026. Divide by 65 for the number of contracts. Source: NSE end of day data, computed by RupeeCase. As of 10 Jun 2026. Open interest counts positions that are still open, and it is not the same as volume. Volume counts the trades done in the session, and a day can have large volume with almost no change in open interest. Open interest rises when two parties open new positions against each other, and it falls when two holders close against each other. When one holder hands a position to another, open interest does not change. A transfer of an existing contract leaves the count alone. Change in OI is the difference from the previous close. A rise in OI with a rising price is usually called a long build up, and a rise in OI with a falling price a short build up. Every contract has a buyer and a seller, so the label names the price move that came with the new contracts, not who is right. The question on [long and short build up](/learn/questions/long-short-build-up) walks through the four patterns. Cumulative OI is the total across the strikes of one chain, or across the expiries of one underlying. It describes how much is open, not who holds which side. Divide the units by 65 to get contracts on the Nifty lot. The chart reads the 30 Jun 2026 Nifty chain as it stood on 10 Jun 2026. Large open interest at a strike shows where many contracts are open. It does not make that strike a wall the index has to respect, and the question on [highest OI strikes](/learn/questions/highest-oi-support-resistance) tests that claim. **Before you trade.** Derivatives trading carries a high risk of loss. SEBI's study "Profitability of Individual Traders in the Equity Derivatives Segment (FY25 to FY26)" (August 2026) found that 87.7% of individual traders in equity F&O made net losses in FY26, with aggregate net losses of Rs 91,685 crore. [Read the SEBI study](https://www.sebi.gov.in/reports-and-statistics/research/aug-2026/study-profitability-of-individual-traders-in-the-equity-derivatives-segment-fy25-fy26-_103835.html) What are open interest, change in OI and cumulative OI?Open interest is the number of contracts still open at the end of a session, which NSE's files count in units, so one lot of 65 units is one contract. Change in OI is how much that number moved since the previous session, and cumulative OI is the total across the strikes of one chain. LGo deeper ## Where Learn teaches this. [Go deeperOpen interest, volume and the four build up patterns7 min, Beginner](/learn/path-13/module-13-3-open-interest-and-build-ups)[Go deeperOI and change in OI on the chain: what they can and cannot tell you8 min, Beginner](/learn/path-15/module-15-2-open-interest-on-the-option-chain) SSources ## Go to the source. 3 sources, NISM the most cited The publisher of each source listed below. Source: Module undefined source list. 1. [NSE option chain page (the screen the school reads only as dated end of day files)](https://www.nseindia.com/option-chain) NSE 2. [SEBI investor education, Understanding derivatives](https://investor.sebi.gov.in/understanding_derivatives.html) SEBI 3. [NISM, Series VIII equity derivatives test objectives (the syllabus names open interest, volume and the put call ratio)](https://www.nism.ac.in/revamp-nism/test-objectives-revised-nism-series-viii-equity-derivatives-certification-examination/) NISM ?Questions people ask ## Related questions. [QuestionVolume or open interest: which matters?Beginner](/learn/questions/volume-or-open-interest)[QuestionLong build-up, short build-up, short covering, long unwinding?Beginner](/learn/questions/long-short-build-up)[QuestionIs the highest call OI strike resistance and the highest put OI strike support?Intermediate, trap check](/learn/questions/highest-oi-support-resistance)[QuestionHow do I read an option chain?Beginner](/learn/questions/how-to-read-option-chain) [All 130 questions](/learn/questions/) Explore next ## Go deeper on this question. * [QuestionWhat is max pain, and does max pain theory work?A short answer with a dated chart](/learn/questions/does-max-pain-work) * [ToolOption payoff builderLegs on a dated Nifty chain, breakevens and charges](/learn/tools/payoff-builder) * [GlossaryInvesting glossary, 230 termsPlain word definitions, and the app’s own](/learn/glossary) Community ## Join my WhatsApp group. Scan the code, fillFill one short form, and join my WhatsApp group. Slides, sources, factsheets and the rebalance logs live there, and members join a daily Google Meet with me. New to RupeeCase? [Getting started](/getting-started) [See the terminal](/terminal) [Sign up for RupeeCase](https://invest.rupeecase.com/signup) [Join the WhatsApp group](https://forms.gle/C6HMtM1Z2GfeocQV7) [One form, one group](https://forms.gle/C6HMtM1Z2GfeocQV7)Scan with your phone camera Education only, not investment advice, a research report or a recommendation to buy, sell or hold any security. RupeeCase (QC Alpha Technologies Pvt Ltd) is not registered with SEBI as an investment adviser or research analyst. Contracts and prices shown are for illustration only, come from NSE end of day files at least 30 days old, and are not recommendatory. Derivatives trading carries a high risk of loss.