Options mechanics
What is Open Interest (OI) and how does it differ from daily transaction volume?
By Easy Money Scanner · Educational reference · Not investment advice
The short answer
Open interest (OI) is the total number of outstanding option contracts for a given strike and expiration that have been opened but not yet closed, exercised, or expired.
How it works
Unlike daily volume, which resets each session, open interest is cumulative and updated once daily by OCC after market close, reflecting net new positions versus closed positions.
An example
If 200 new XYZ 50 calls are bought to open and 50 existing contracts are sold to close in one day, open interest changes based on the net opening versus closing activity.
Risk & limitations
High volume with low open interest can indicate day-trading activity rather than sustained institutional positioning, so consider both figures together, not volume alone.
Examples are hypothetical, not trade recommendations. US contract and regulatory references do not automatically apply in Canada. Rules, margin requirements and broker policies can change; confirm them with the relevant authority and your broker.