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The put/call ratio divides put volume by call volume for a stock, an index, or the whole market. A ratio of 1.0 means puts and calls traded in equal size; above 1.0 means more puts traded; below it, more calls.

It compresses a full day of options volume into one number, which makes it a quick gauge of which side of the chain was busier. What it shows is lopsided flow, not intent — selling a put and buying a put print the same way, so a high ratio cannot say whether the crowd was seeking protection or supplying it.

Like most flow measures, it is most readable against its own history for the same underlying.

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A worked example with round numbers:

• Puts traded: 800,000 contracts
• Calls traded: 500,000 contracts
• Put/call ratio: 800,000 ÷ 500,000 = 1.6

Whether 1.6 is notable depends entirely on the baseline. For a broad index, ratios above 1.0 are routine because institutions steadily buy index puts as portfolio insurance; for a single stock that usually runs near 0.5, the same 1.6 would be a sharp departure. The number becomes information only when set against the same underlying's typical range.

Two versions exist. The volume ratio uses the day's trading and moves quickly; the open-interest ratio uses outstanding contracts (see open interest) and drifts slowly. They can disagree: a burst of put trading lifts the volume ratio immediately while barely moving the open-interest ratio if the positions were closed the same day.

The ratio also ignores size and price. 800,000 puts at far-out-of-the-money strikes can represent less premium than 500,000 at-the-money calls, so two markets can share a ratio of 1.6 and look nothing alike underneath. Current ratios across the market appear on the activity page.

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Two formal variants exist. The volume ratio is the day's total put volume divided by the day's total call volume; the open-interest ratio divides outstanding put contracts by outstanding call contracts at a point in time. Both are dimensionless, bounded below by zero, and unbounded above. Options Band computes them from delayed Cboe data.

The central misconception is reading a high ratio as bearish consensus. Every put that traded had a buyer and a seller, and the ratio counts the print, not the motive: put buying to hedge stock, put selling to collect premium, and the put leg of a spread are indistinguishable in the total. Market folklore also treats extreme readings as contrarian signals; Options Band presents the ratio as a descriptive statistic and leaves interpretation to the reader.

Limitations: aggregation discards strike and expiration structure, so very different chains can share one ratio; premium is ignored, so many cheap far-out-of-the-money contracts outweigh fewer expensive ones in the count; and on thinly traded underlyings a single large order can move the day's ratio several fold, which makes single-name readings far noisier than index-level ones.