What is open interest in the stock market?

Open interest (OI) is the total number of outstanding derivative contracts — futures or options — that have not yet been settled or expired. Each open contract represents one buyer and one seller who have not yet closed their positions. OI increases when new contracts are created and falls when existing contracts are closed or expire.

What is the full form of OI?

The full form of OI is Open Interest. It refers to the total number of active, unsettled derivative contracts in the market at any given time. In India, NSE publishes OI data for all futures and options contracts on indices like Nifty 50 and Bank Nifty, as well as for individual equity derivatives.

How is open interest different from trading volume?

Trading volume counts contracts bought and sold within a single session — it resets to zero each day. Open interest counts contracts that remain active and unsettled — it carries forward from session to session. OI only increases when a brand new contract is created between a new buyer and a new seller.

How do traders use OI data in options trading?

Traders look at OI in the options chain to identify where large positions are concentrated. High call OI or put OI at a specific strike may indicate heavy positioning by market participants. The put-call ratio (PCR), calculated by dividing total put OI by total call OI, is one of the most common indicators derived from OI data in Indian markets.

What does rising OI with rising price indicate?

When both price and OI rise together in a futures contract, it generally suggests that new money is entering the market on the long side. This is often read as a sign of trend strength. However, OI-price combinations are observations, not definitive signals. They should be used alongside other market data for context.

Open Interest (OI) in Stock Market: Full Guide

Open Interest (OI) in the Stock Market: A Complete Guide

Team Sahi

Published: 26 Feb 2025, 01:10 PM IST (1 year ago)

Last Updated: 18 Mar 2026, 05:30 AM IST (2 weeks ago)

Open Interest (OI) in the stock market is the total number of outstanding derivative contracts — futures or options — that have been entered into but not yet settled or closed at the end of a trading session. Rising open interest alongside rising prices typically confirms a bullish trend, indicating new money is entering the market; falling open interest with falling prices confirms a bearish trend as positions are being closed. OI measures overall market participation and liquidity rather than the directional bias of individual trades.

Open interest, commonly written as OI, is the total number of outstanding derivative contracts that have not been settled. It applies to both futures and options.

OI is one of the most watched data points in Indian derivatives markets. It tells you how many contracts are currently active in the market.

OI Full Form and Meaning

The full form of OI is Open Interest. "Open" means the contract is still active. "Interest" refers to the number of contracts currently held by market participants.

Every futures or options contract needs a buyer and a seller. When a new contract is created, OI increases by one. When a contract is closed or expires, OI decreases by one.

Open Interest vs Trading Volume

Trading volume counts contracts traded in a session. OI counts contracts still open at the end of the session. They are different numbers.

How OI Changes

OI increases when a new contract is created. OI decreases when an existing contract closes. OI stays flat when an existing participant transfers their position to a new participant.

Open Interest in Options

In Indian options markets, OI data is available for each strike price. The NSE publishes a full options chain showing the OI for every call and put option on Nifty, Bank Nifty, and individual stocks.

OI Data and the Options Chain

The options chain on NSE shows both call OI and put OI at each available strike price. It also shows the change in OI from the previous session.

Put-Call Ratio and OI

The put-call ratio (PCR) uses OI data directly: PCR = Total Put OI ÷ Total Call OI. A PCR above 1 means more put OI than call OI, suggesting more downside hedging. A PCR below 1 means more call OI.

OI and Market Liquidity

High OI at a strike price means more participants are present. This tends to make that contract more liquid. Indian traders often prefer to trade near strikes with the highest OI.

Futures Open Interest and Rollovers

In the futures market, OI drops sharply near expiry. A rollover happens when a trader closes their current-month position and opens an equivalent position in the next-month contract.

FII and DII OI Data

SEBI requires disclosure of FII and DII positions in the derivatives market. NSE publishes this data daily. Traders watch FII OI data closely for institutional positioning signals.

Limitations of OI Data

OI does not tell you the direction of a trade. Large OI at a strike is a data point — not a signal on its own. OI works best when read alongside price action, volume, India VIX, and other market data.