What is Total Call OI (Open Interest)? Total Call OI (Open Interest) is the options strike with the largest number of call options. Why does Total Call OI (Open Interest) matter? This dynamic can cause stocks to pin a level or create resistance for the underlying stock. How to use Total Call OI (Open Interest) Consider it as an upside target or resistance point when trading the stock. Interested in learning more? Related articles What is Top Put OI (Open Interest)? What is Gamma in Next Expiration? What is Gamma, Market Gamma and/or Total Market Gamma? What is Highest Gamma Expiration Date? What is Reference Price/Ref Price?