What is Open Interest (OI)? The Concept Explained
Open interest is the number of derivative contracts that are currently open and not yet closed or settled. It counts standing positions rather than daily activity. Open interest rises when new positions are created and falls when existing ones are closed.
Open interest is one of the most quoted numbers in derivatives, and one of the most often misapplied. Before reading anything into it, it helps to be precise about what the number counts.
This article stays with the concept itself. How to interpret it is a separate question, and the answer differs between futures and options, so those are covered in their own guides.
Key Takeaways
- Open interest counts contracts that are still open.
- It rises only when a new position is created.
- It falls when an existing position is closed.
- A trade between two existing holders leaves it unchanged.
- It is different from volume, which resets each day.
What exactly is being counted?
Every derivative contract has a buyer and a seller. Open interest counts that pair once, not twice. If one lot changes hands and both sides are opening new positions, open interest increases by one. The number therefore represents how many contracts are still live in the market.
When does open interest change?
The direction of the change depends on whether each side is opening or closing. There are three cases, and knowing which one applies is the whole of the concept.
| Buyer | Seller | Effect on open interest |
|---|---|---|
| Opening a new position | Opening a new position | Rises by one contract |
| Closing an existing position | Closing an existing position | Falls by one contract |
| Opening a new position | Closing an existing position | No change, the position transfers |
The third row explains why heavy trading does not always change open interest. If positions are simply passing from one holder to another, the total number outstanding stays the same.
How is open interest different from volume?
Volume counts how many contracts traded during the session and starts again at zero the next day. Open interest counts what remains outstanding and carries forward. A session can have very high volume with almost no change in open interest, which tells you activity was mostly intraday.
| Measure | What it counts | Resets daily |
|---|---|---|
| Volume | Contracts traded in the session | Yes |
| Open interest | Contracts still open | No, it carries forward |
Why the number is worth watching
Open interest shows how much commitment sits behind a contract. A rising figure means money is entering, while a falling figure means participants are stepping away. That is as far as the raw number goes. Turning it into a view about direction requires knowing whether you are looking at futures or options, because the two are read in completely different ways.
For futures, open interest is combined with the price move to classify the buildup. For options, the same rise in open interest is usually about writing rather than buying, so it points to expected barriers instead. Those two readings are covered separately.
Curious to try F&O with full options data yourself? Head to Stockk, open a quick demat account, and use the Knowledge Center whenever you need a refresher.
Futures and Options are leveraged products and carry a high risk of loss that can be more than the money you put in. This article is only for learning and is not a recommendation to trade in derivatives.
Frequently Asked Questions
Does open interest count both the buyer and the seller?
No. Each contract has a buyer and a seller, and open interest counts that pair once. One lot opened by both sides adds one to the total.
Why does open interest sometimes stay flat on a busy day?
Because a position can transfer between participants. When one trader opens and another closes, the total number of live contracts does not change.
How is open interest different from volume?
Volume counts contracts traded during the session and resets daily, while open interest counts contracts still outstanding and carries forward.
Does rising open interest mean the market will go up?
Not on its own. It only shows that fresh positions are being created. The direction it implies depends on whether you are reading futures or options.
Where do I learn to interpret open interest?
Futures and options are read differently, so each has its own guide.
Investments in securities market are subject to market risks. This article is for educational purposes only and does not constitute investment advice.
INDIRA SECURITIES PRIVATE LIMITED : SEBI REG. NO.: INZ000188930, NSE TMID: 12866, BSE TMID: 663, CDSL DPID: 17000, MCX TM ID: 56470, NCDEX TM ID: 01277, CDSL REG.NO.: IN-DP-90-2015, CIN:U67120MP1996PTC085111, RA SEBI REG. No.: INH000023269, IA SEBI REG No.: INA000021410
