Glossary
Open interest
The number of option or futures contracts outstanding that have not yet been closed, exercised or expired.
On this page
Open interest is the total number of derivative contracts, such as options or futures, that are currently open: created by a buyer and a seller and not yet closed out, exercised, assigned or expired. Unlike volume, which counts every contract that changes hands during a day, open interest measures how many positions exist at a point in time. Traders use it to judge how active and liquid a contract is and whether money is flowing into or out of a market.
How it changes
Open interest moves only when a trade opens or closes positions. Every contract has one long and one short side, so each open contract counts once.
For US listed options, open interest is published once a day, based on the previous day's closing positions, so it does not update intraday.
How traders read it
- Liquidity: strikes and expirations with high open interest usually have tighter bid-ask spreads.
- Positioning: rising open interest with a rising price is often read as new money joining the move; falling open interest suggests positions are being closed.
- Concentration: large open interest at a particular strike can attract attention near expiration, as hedging by dealers may influence the underlying.
Open interest does not say whether buyers or sellers initiated the positions, so it cannot by itself show whether the market is bullish or bearish.