Open Interest (OI) is one of the most important concepts in derivatives trading, yet it is often misunderstood by beginners. Many traders focus only on price movement and overlook the information hidden within market participation data. Open Interest helps traders understand how many active contracts currently exist in the market.

What Is Open Interest?

Open Interest refers to the total number of active derivative contracts (in futures or options) that have not been closed, settled, or exercised. Unlike trading volume, which measures how many contracts changed hands during a specific session, Open Interest measures ongoing market participation and capital commitment.

How Open Interest Is Created

Open Interest increases when a new buyer and a new seller create a fresh contract. It decreases when both parties execute orders to close their existing positions. If one trader transfers an open position to another trader, Open Interest remains identical of course, because no new contract came into existence. Studying these mechanics is essential before interpreting complex option chain tables.

Open Interest in Option Chain Analysis

Option chain analysts frequently study Open Interest concentrations to understand where market participants are positioning themselves. Large accumulations of outstanding put-side contracts are frequently monitored as potential support zones, while heavy call-side concentrations are observed as potential resistance ceilings. Always combine OI evaluations with price action, trade volume, and proper charts before forming trading plans.