What is open interest?
Open interest counts futures contracts that are still open, while trading volume counts every contract traded during a period.
Version 1
GlossaryOpen interest is the number of futures contracts that remain open. It grows when new positions are created and falls when positions are closed.
Imagine one $100 position being opened, closed and reopened 20 times. That activity can create much more than $100 of trading volume even if only one $100 position remains open at the end.
A little more technical
Volume counts contracts traded during a period. Open interest counts contracts that have not been closed or settled. Comparing the two can help show whether a market is building lasting positions or turning positions over quickly.
Common misunderstanding
High volume with lower open interest can suggest heavy churn, but it does not prove wash trading or tell us why each trader acted.
Source: CME Group’s open-interest lesson explains the difference between open interest and volume.