Guide · Markets
What Is Open Interest? Reading Positioning Behind the Price
Open interest is one of the most misunderstood numbers on an options or futures chain. It's not volume — here's what it actually counts.
Open interest (OI) is the total number of options or futures contracts currently held open — meaning contracts that have been opened by a trade but not yet closed, exercised, or expired. It's a running headcount of live, unsettled positions in a given contract, updated once per trading day.
This makes it fundamentally different from volume, which counts every trade executed during a session regardless of whether it opened a new position or closed an existing one. A single trade can leave open interest completely unchanged: if one trader closes a position by selling to a second trader who is opening a brand new one, volume rises by one contract while OI stays flat, since one contract closed as another opened.
Rising open interest alongside a rising price is generally read as new money confirming the move — fresh positions are being opened in the direction of the trend. Rising open interest alongside a falling price suggests the same thing in reverse: fresh short or put positions building. Falling open interest, regardless of price direction, suggests existing positions are being closed out rather than new conviction entering the market.
Options chains also use open interest to gauge where the market has concentrated its bets — strike prices with unusually high OI often act as informal support or resistance near expiration, as market makers hedge their exposure to those contracts. It's a layer of context worth learning to read before it factors into a live options trade.