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. Related articles What is Top Put OI (Open Interest)? When do the Equity Hub™ levels update?