Open Interest vs Volume
Volume measures activity; open interest measures commitment — reading both together is essential for interpreting NSE F&O price moves.
Definition
Open interest (OI) is the total number of outstanding derivative contracts — futures or options — that have not yet been settled or closed. It increases when a new buyer and a new seller enter a contract together, and decreases when an existing holder squares off their position. Volume, by contrast, is simply the count of contracts that changed hands during a given session, regardless of whether those trades opened new positions or closed existing ones. Volume resets to zero at market open each day; OI carries forward until contracts expire or are closed. See also open interest and change in OI for deeper coverage of each metric individually.
Why it matters
The combination of price, volume, and OI is far more diagnostic than any single metric alone. Four canonical interpretations drive much of NSE F&O analysis. First, rising price with rising OI and strong volume signals fresh long positions entering — a bullish confirmation, often called a long buildup. Second, falling price with rising OI and volume points to fresh shorts — a bearish signal. Third, rising price with falling OI suggests short-covering rather than new conviction, a weaker signal that may stall quickly. Fourth, falling price with falling OI means longs are unwinding — also potentially exhausting.
On NSE, where weekly expiries for Nifty (Thursday), Bank Nifty (Wednesday/Thursday), Fin Nifty and Midcap Nifty create multiple live series simultaneously, OI concentrated in certain strikes reveals where market participants have placed large directional bets. Volume spikes in those same strikes alert traders to fresh activity rather than passive rollover.
How it works
Every derivative trade involves a buyer and a seller. If both are initiating new positions, OI rises by one contract and volume rises by one. If one party is opening a new position and the other is closing an old one, OI stays flat but volume still rises. If both parties are closing existing positions, OI falls by one and volume still rises. This asymmetry explains why volume always equals or exceeds the change in OI over any period, and why high volume with flat OI tends to indicate churning — lots of intraday noise, limited new conviction.
Example
Suppose Bank Nifty futures show volume of 1,20,000 contracts on a given Thursday, but OI rises by only 8,000 contracts from the previous close. This tells us that most of the trading was position-churning — existing holders selling to new holders, or day-traders squaring off by end of session. Now suppose the next day volume is only 60,000 but OI rises by 25,000. That smaller volume session actually reveals far more new committed money entering the market, making it the more directionally significant day despite lower raw activity.
See OI and volume live
TradePulse's option chain shows OI, change in OI, and volume strike-by-strike in real time.