How to Read Open Interest in an Options Chain: A Beginner’s Guide

Learn how to read open interest in an options chain, compare call and put OI, understand OI changes, and use OI with volume and price data.

If you have ever opened an options chain and felt overwhelmed by rows of strikes, prices, volume, implied volatility, and Greeks, you are not alone. One of the most useful numbers you will see is Open Interest (OI) , but it can easily be misunderstood. Learning to read open interest can help you understand where existing options positions are focused and provide you with additional insights into the options market. The key is to remember that OI is not a crystal ball. Open interest shows you how many option contracts are still active for a specific strike price and expiration date. It does not reveal who holds those contracts, why they bought them, or whether the market trends are bullish or bearish. When you combine OI with volume, price action, implied volatility, expiration, and bid-ask spreads, analyzing an options chain becomes much more effective. What Is Open Interest in Options Trading? Open interest shows the total number of active option contracts for a specific option series. An option series is defined by details such as the underlying security, strike price, expiration date, and whether the contract is a call or put. If there are 5,000 contracts open at a certain strike price, the options chain will usually show an open interest of 5,000 for that contract. Think of open interest as a tally of contracts that have not been closed, exercised, or removed from the open position pool. It differs from the number of shares traded in the underlying stock and from the number of option contracts traded during the current session. This distinction is important because options trading involves two sides to each contract. If one trader buys an option to open a position and another trader sells an option to also open a position, a new open contract is created, increasing open interest by one contract. If both parties are closing existing positions, open interest decreases by one contract. If one participant is opening a position and another is closing, the transaction can change ownership of an existing position without altering the total open interest. That is why open interest should not be confused with daily trading activity. The Options Industry Council states that volume measures trading activity during a session, while open interest reflects the contracts that remain open. Open interest is calculated after the relevant trade and clearing information is processed, so it is not just a live count of every trade happening throughout the day. For beginners, the easiest way to think about it is this: volume shows what has traded, while open interest shows what is still open . Where Do You Find Open Interest in an Options Chain? An options chain usually organizes contracts by expiration date and strike price. Calls typically appear on one side of the chain, while puts are on the other. The strike price is positioned between them, making it easy to compare calls and puts at the same strike. Depending on the broker or options platform, you might see