Definition · updated 2026-10-22
Volume vs open interest
Volume is the number of contracts traded today; open interest is the number of contracts that exist and remain open, updated once a day. Volume above open interest on a strike means new positions are being built, not old ones closed, which is the pattern behind most unusual-activity alerts.
See it live: /most-active-options.
A worked example
A strike opens the day with 2,000 contracts of open interest and trades 9,000 contracts. At most 2,000 of those could be closing trades, so at least 7,000 are new positions: tomorrow's open interest will be higher. A strike with 50,000 open and 3,000 traded tells you nothing new; the book is standing and today's trades could all be rolls or closes.
Volume resets every session and prints through the day; open interest is published by the OCC before the next open, so it always lags by a session.
Where each one matters
Volume drives the flow tape, the most-active list and the put/call ratio by volume. Open interest drives everything positional: gamma exposure, max pain, the call and put walls and the put/call ratio by open interest. A reading that uses the wrong one, such as a 'sweep' sized off a stale day block, is the most common error in retail options analysis.
Frequently asked questions
- Is high volume or high open interest better for liquidity?
- Both, but for different reasons: open interest tells you the market exists and spreads are usually tight; volume tells you you can get out today. A contract with large open interest and no volume can still be hard to exit at a fair price.
- Can volume exceed open interest?
- Yes, and it is the signal traders look for: more contracts traded than were open means new positions. The volume/OI column on the most-active list flags exactly that.
- When does open interest update?
- Once a day, before the open, for the previous session's trades. Intraday you see volume; the open-interest effect of those trades shows up the next morning.