Open Interest vs Volume in Options
Confusing open interest with volume is the most common beginner error in reading an option chain.
What is the difference between open interest and volume?
Volume counts contracts traded during the current session and resets to zero each morning. Open interest counts contracts currently outstanding and carries forward day to day until those positions close. Volume therefore measures activity, while open interest measures the standing positions that still require dealer hedging.
Why does positioning analysis use open interest?
Dealer hedging obligations come from contracts that remain open, not from contracts that were traded and closed within the same session. Gamma exposure therefore multiplies gamma by open interest, because only outstanding contracts create the standing forced hedging flow that actually moves the underlying.
When is volume more useful than open interest?
Volume is more useful for spotting fresh intent within the session, because open interest updates only once per day after the close. A large sweep shows in volume immediately, while the positioning effect appears in open interest the following morning.
Frequently asked questions
Can volume exceed open interest?
Yes. Heavy same day opening and closing of positions can push volume well above open interest, which is common on 0DTE contracts.
How often does open interest update?
Open interest is published once per day by the clearing house, reflecting the prior session's closing positions.