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Options volume vs. open interest: what each number measures
Separate today's contract turnover from outstanding positions and learn why volume does not translate directly into next-day open interest
Prepared by Mark · Primary sources below
Direct answer
Option volume counts contracts traded during a session, while open interest counts contracts that remain open after clearing. One contract can trade several times and add several units of volume without creating the same increase in open interest. Open interest rises only when both sides open, falls when both close, and can remain unchanged when an opening position replaces a closing one
Read volume as activity within the trading day
Volume resets for each session and records completed contracts, not unique traders or directional conviction. A high-volume series may be actively opening, closing, rolling, or transferring risk. Comparing volume with liquidity, spreads, and the underlying market is more useful than treating a large print count as a standalone signal
Read open interest as positions surviving clearing
OCC calculates open interest after exchanges report opening and closing activity and exercised contracts are removed. That is why the reliable figure is generally a next-day result rather than a live counter. Two opening sides increase it, two closing sides reduce it, and one opener matched with one closer leaves the total unchanged
Avoid converting the ratio into a forecast
Volume greater than open interest can highlight unusual turnover, but it does not reveal who initiated each trade, whether positions were opened, or where the underlying will move. Check consecutive days, strike and expiration concentration, executable quotes, and related contracts before forming a market-activity hypothesis
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