How to read an option chain: open interest, PCR and Max Pain
What positioning data on an option chain actually measures, how traders read it, and the limits every one of these numbers carries.
Updated 2026-10-07
The layout, once
An option chain shows one underlying and one expiry. Strikes run down the middle; calls sit on one side and puts on the other. Each row carries the premium, the volume traded, the implied volatility and the open interest for that strike. The row nearest the current price is the at-the-money strike, and strikes are shaded by whether they are in the money. If premium and moneyness are new to you, the basics guide covers them first.
Open interest: contracts still open
Open interest (OI) is the number of contracts at a strike that have been opened and not yet closed. It is not the same as volume. Volume counts every trade today, including trades that open and close positions within the hour; OI counts what is still standing at the end. A strike can trade heavily and see its OI barely move.
Traders read large OI as interest the market has committed to. A strike with heavy call OI above the current price is often described as resistance, and heavy put OI below it as support, on the reasoning that option sellers, who usually hold the larger positions, will defend those levels. It is a useful map of where positions are concentrated. It is not a wall: price moves through heavy OI strikes regularly, and the positions there are then adjusted or closed.
Change in OI: the part that moves
The total says where positions sit; the change in open interest during the session says where they are being added or removed today. Read alongside price, it separates four situations: price up with OI rising suggests new longs, price up with OI falling suggests shorts closing, price down with OI rising suggests new shorts, and price down with OI falling suggests longs closing. These are interpretations, not facts: the chain records that contracts were opened, never who opened them or why.
The put-call ratio
The put-call ratio (PCR) divides total put open interest by total call open interest for an expiry. A PCR above 1 means more puts are open than calls; below 1, the reverse. It is commonly read as a sentiment gauge, and just as commonly read in two opposite ways: a high PCR as fear, or as put writers confident enough to sell protection. Both readings are in circulation because neither is reliable on its own.
The honest use of PCR is as context. A reading that moves sharply from its own recent range says positioning changed, which is worth knowing. A single PCR number on its own says very little about where the index goes next.
Max Pain
Max Pain is the strike at which the total value of all open options, calls and puts together, would be lowest if the index expired there. It is the expiry price that would cost option buyers the most in aggregate. The theory attached to it is that the index tends to drift toward Max Pain into expiry.
Treat that theory with care. Max Pain is a calculation on today's open interest, and open interest changes through the session, so the strike moves too. Some expiries do settle near it; many do not. It is a reference point for where the option book is balanced, not a forecast.
Putting it together without fooling yourself
Read positioning data as a description of the present: where contracts are concentrated, where they are being added, how the book is balanced. Pair it with what the Greeks say about how the premiums you care about will respond. And when a pattern seems convincing, test it: the simulator replays recorded sessions, so you can watch how the chain looked on days the index ran straight through a supposed wall.
The option chain in EzyOptions draws OI as depth bars per strike and computes PCR and Max Pain across the whole chain as it updates, so these numbers are visible without working them out by hand.
Questions people ask
How do you read an option chain?
Pick one underlying and expiry. Find the at-the-money strike nearest the current price, then look across each row at premium, implied volatility and open interest for calls and puts. Large open interest shows where positions are concentrated; the change in open interest shows where they are being added or closed today.
What does a high put-call ratio mean?
It means more put contracts are open than call contracts for that expiry. Traders read it both as fear and as confident put writing, which is why it is a weak signal on its own. A PCR that moves sharply away from its own recent range is more informative than any single reading.
Is Max Pain accurate?
Max Pain is accurate as a calculation: the strike where open options would be worth least at expiry. As a prediction it is unreliable. It is computed from open interest that changes through the session, so the strike itself moves, and many expiries settle well away from it.
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Educational content only: not investment advice. You are responsible for your own trading decisions.