Direct Answer
Put volume divided by call volume on options of the S&P 500 index (SPX), as published by Cboe. SPX options are used heavily by institutions for hedging and for expressing index views. A higher ratio indicates more put trading and a lower one more call trading.
SPX Put/Call Ratio: Formula, Meaning, Signals, Examples and How to Use It
How Is SPX Put/Call Ratio Calculated?
Put volume divided by call volume on options of the S&P 500 index (SPX), as published by Cboe. SPX options are used heavily by institutions for hedging and for expressing index views.
Formula: SPX put/call = SPX put volume / SPX call volume
Inputs:
- Daily put volume on SPX options
- Daily call volume on SPX options
- Whether SPXW weeklies are included
Worked example. If 1,200,000 SPX put contracts and 1,000,000 call contracts trade in a day, the ratio is 1.20. The inputs are illustrative numbers, not market data.
Reading it. A higher ratio indicates more put trading and a lower one more call trading. Because SPX puts are used to hedge portfolios, the ratio is often above 1 and is judged relative to its own recent history.
Limits. The reading mixes hedging with speculation, so the same volume can have opposite meanings. Short-dated options now make up a large share of volume, which changes what the ratio reflects.
What is SPX Put/Call Ratio?
Put volume divided by call volume on options of the S&P 500 index (SPX), as published by Cboe. SPX options are used heavily by institutions for hedging and for expressing index views.
How to use SPX Put/Call Ratio
A higher ratio indicates more put trading and a lower one more call trading. Because SPX puts are used to hedge portfolios, the ratio is often above 1 and is judged relative to its own recent history. A reading alone is never a buy or sell signal; it needs context from price structure, volume, volatility and the broader market regime.
Strengths
- Limiting the count to SPX options isolates one of the most heavily traded index option products.
- SPXW weekly expirations can be included or excluded as an input, so the effect of short-dated volume can be checked.
- Reproducible when the formula and data convention are fixed.
Weaknesses and limitations
- Because SPX options are cash settled and large in notional, one big institutional trade can move the day's ratio.
- The level typical for SPX differs from that of the equity-only ratio, so numbers from the two are not interchangeable.
- Correlated indicators can create false confidence by repeating the same underlying information.
Editorial and risk note
This page is educational content, not individualized investment advice. It should not imply guaranteed prediction, accuracy or outperformance.
Frequently Asked Questions
Is SPX Put/Call Ratio a buy or sell signal?
No. A higher ratio indicates more put trading and a lower one more call trading. The reading mixes hedging with speculation, so the same volume can have opposite meanings. A trade built on it still needs a trigger, an invalidation rule, a position size and realistic execution assumptions.
What is the best setting for SPX Put/Call Ratio?
SPX Put/Call Ratio is computed from daily put volume on SPX options; daily call volume on SPX options; whether SPXW weeklies are included, so the choices that matter are the data convention and the window it is read over. Test those across instruments, regimes and out-of-sample periods instead of fitting one historical winner.
Can SPX Put/Call Ratio be used by itself?
The reading mixes hedging with speculation, so the same volume can have opposite meanings. Short-dated options now make up a large share of volume, which changes what the ratio reflects. For that reason it is read next to measures of direction, participation, valuation, liquidity and risk, not alone.
Does SPX Put/Call Ratio work on every timeframe?
The calculation (SPX put/call = SPX put volume / SPX call volume) can be run on any bar size, but behavior is not portable: a reading on a five-minute chart describes a very different market window from the same reading on a daily chart. Validate the exact timeframe before relying on it.
Why does SPX Put/Call Ratio give false signals?
Because SPX options are cash settled and large in notional, one big institutional trade can move the day's ratio. The level typical for SPX differs from that of the equity-only ratio, so numbers from the two are not interchangeable. Lag, noise and regime changes add to this, because market participants react to new information after the reading is calculated.
How should SPX Put/Call Ratio be backtested?
Rebuild SPX Put/Call Ratio from daily put volume on SPX options using point-in-time data, write the rules before testing, include delisted securities where relevant, model realistic fills and costs, reserve a validation sample and compare with a simpler baseline.