What is the put/call ratio, and how do you read it?

The put/call ratio is the number of puts divided by the number of calls for a set of options. Measured by volume, it compares contracts traded in one session; measured by open interest, it compares contracts still open. A ratio above 1 means more puts than calls, and below 1 means more calls than puts. Neither version says who bought or sold, or why, so it is read against the same symbol's own history and never as a signal on its own.

What the put/call ratio measures

Cboe publishes the put/call ratio every trading day, split by segment into total, equity and index ratios.¹ The definition is simple: put volume divided by call volume for a group of options over a period. Volume counts contracts traded. It does not say whether each trade opened or closed a position, or who was the buyer and who was the seller.

There are two common versions:

• The volume ratio uses put volume and call volume. It describes one session of trading.
• The open-interest ratio uses open interest, the number of contracts still open. The Options Industry Council puts the difference this way: volume captures activity within a session, whereas open interest reflects the cumulative number of contracts still open.² OCC counts open interest once a day from the exchanges' trade reports, which detail every opening and closing transaction, and exercised and assigned contracts drop out of it.²

A put gives its holder the right to sell the underlying shares at the strike, so puts are the contract people use to protect shares they own. That one fact shapes most of what the ratio can and cannot tell you.

The worked example: Friday 2026-10-16

The figures below come from CaymanBot's delayed options dataset for the session of Friday 2026-10-16. Volume is the session total as of the 16:00 ET close.³ Open interest comes from the GEX snapshot in the same file, as of 15:45 ET. Open interest is a once-a-day count, so that snapshot may not include the trades made during the session. The totals cover the contracts in CaymanBot's dataset for SPY.

Step 1: the volume ratio

Divide put volume by call volume:

That is about 1.44 puts traded for every call during the session. Our put/call ratio page shows this ratio for a ticker.

Step 2: the open-interest ratio

Divide put open interest by call open interest:

That is about 1.67 open puts for every open call.

Step 3: compare the two

The open-interest ratio (1.671) is above the volume ratio (1.438). In plain terms, the puts that were already open outweighed the open calls by more than that one session's trading did. The two numbers answer different questions: one is about a day's activity, the other is about positions built up over many sessions. Our guide to options volume vs open interest walks through that difference in more detail.

The open-interest figures here are the same ones that feed our gamma exposure maps; the post on what gamma exposure is and how to read it uses the same snapshot data. Open interest also drops when contracts expire, which our post on what happens to gamma exposure after monthly expiration works through.

SPY next to two single stocks

The same session, from the same dataset, for TSLA⁴ and META:⁵

The arithmetic for TSLA:

TSLA's open puts and open calls were nearly even, while its session traded more calls than puts.

And for META:

META runs the other way from SPY: its open-interest ratio sits below its volume ratio.

SPY sits above 1 on both measures, while TSLA and META sit below 1. That fits SPY's use as a hedge for whole portfolios. It describes one session, and it says nothing about anyone's view of where any of these prices goes.

How to read it, and its limits

The ratio is a count, so it inherits every blind spot of the counts behind it:

1. Puts are often hedges. Someone who owns shares and buys a put to protect them adds to put volume. That trade is insurance on a position, and the ratio cannot tell it apart from any other put trade.
2. Sold puts count too. Every contract traded has a buyer and a seller, and volume counts that contract once. A put sold by an investor collecting premium raises the ratio exactly as much as a put bought for protection.
3. Opening and closing look the same. Volume does not say whether a trade opened a new position or closed an old one, so a busy day of puts can be people taking protection off as easily as putting it on. Our post on what buy to open and sell to close mean covers those terms.
4. Index and ETF options run higher. SPY options are often used to hedge stock portfolios with puts, one common explanation for why an index ETF's ratio tends to run higher than a single stock's. Comparing SPY's 1.438 with TSLA's 0.608 compares different kinds of users, not opinions.
5. One day is noise. A single session's ratio moves with expirations, hedging schedules and a few large trades. Read it against its own history for the same symbol, over many sessions.

For the same reasons, a high ratio does not mean sell and a low one does not mean buy. The ratio describes how puts and calls were traded or held, and it is most useful as context next to the strikes, expirations and sizes that make it up.

How to practice this

Pick one symbol and write down its volume ratio and open-interest ratio after a few sessions, then compare each day with the ones before it rather than with another ticker. CaymanBot's $100K paper account lets you practice reading options activity without real money at stake. In the first two Learning Mode stages, each trade on the feed comes with a plain-English sentence you can check against the strike, expiry and premium. A free account shows options data delayed 16 minutes (60 minutes without an account). New accounts start with a 14-day Premium trial.

Educational only, not investment advice.