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Open interest and PCR: context, not a prediction

Learn what open interest and the put-call ratio can tell you, what they cannot, and why expiry and missing data matter.

Open interest (OI) measures outstanding option contracts. It is different from volume: a contract may trade several times during a session, while open interest depends on whether transactions open or close positions.

What the put-call ratio measures

An OI put-call ratio divides total put open interest by total call open interest for a defined underlying and expiry. A volume put-call ratio uses volume instead. Always label which ratio you mean. If call OI is zero or missing, an OI ratio is undefined.

A small example

For a hypothetical complete expiry with 12,000 put contracts and 10,000 call contracts outstanding, OI PCR is 1.2. This describes the balance of outstanding contracts. It does not mean a 120% chance of a rise, and it does not identify who bought or sold those contracts.

Why a large OI strike is not a guaranteed wall

Positions can be hedges, spreads or directional trades. A large concentration may be useful context, but prices can move through it. Interpreting it requires price behavior, liquidity, changes over time and knowledge of the data source.

Compare like with like

Use the same underlying, expiry, units, strike coverage and update schedule. Comparing a few near-the-money strikes against yesterday's full chain can create a misleading change. Missing OI must remain missing rather than silently becoming zero.

How Celesys displays it

The explorer shows a snapshot OI ratio only when both sides have OI at every returned strike and call OI is positive. Even then, it is calculated from provider-returned contracts, not proof of complete exchange coverage. Celesys does not turn PCR into a standalone buy or sell signal.

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