Open Interest

The total number of outstanding futures or options contracts that have not been settled or closed — a measure of market participation and liquidity.

Open interest (OI) counts the total number of contracts currently held by market participants. Each open contract represents one long position and one short position. Open interest increases when a new contract is created — a buyer who doesn't already own a contract and a seller who doesn't have an existing short position open a new position together. Open interest decreases when a contract is closed — an existing buyer sells to an existing seller, net of new openings.

Open interest is distinct from trading volume. Volume counts every transaction in a session; open interest counts only contracts that remain open at the end of the session. High volume with declining open interest may indicate closing activity (existing participants exiting) rather than new money entering. Rising open interest confirms new money is flowing into a trend; declining OI suggests the trend is driven by closing activity rather than fresh conviction.

In options markets, open interest at specific strike prices provides insight into where large positions have been built. Very high open interest at a particular options strike can create a "gravitational" effect near expiration — market makers with large open option positions may hedge in ways that cause the underlying to pin near the high-OI strike, a phenomenon called "max pain" theory. While not infallible, significant concentrations of open interest are worth monitoring.

This definition is for informational and educational purposes only. Nothing on Finance Compass constitutes financial, investment, or trading advice. Always conduct your own research and consult a qualified professional before making financial decisions.