The put/call ratio divides the volume of puts traded by the volume of calls over a period. More puts than calls (ratio above 1) suggests traders are buying downside protection or betting bearish; more calls (ratio below 1) suggests bullishness or speculation. It is a crude thermometer for market sentiment.
Why extremes are contrarian
The counterintuitive part: extreme readings often mark turning points, not continuations. When the ratio spikes very high - everyone piling into puts - fear may be peaking, and washed-out markets tend to bounce. When it drops very low - everyone chasing calls - complacency is high and the tape is vulnerable. Extremes read as contrarian; the middle is just noise.
Which ratio you're looking at
There are several: equity-only, index-only, and total. Index puts are often bought as portfolio hedges, not directional bets, so an index-heavy ratio can look bearish when it is really just insurance. Knowing the source matters before you draw a conclusion.
The put/call ratio is a crowd mood ring - loudest exactly when the crowd is most wrong.
How to actually use it
Treat it as context, not a trigger - one input alongside the VIX, dealer positioning, and structure. A sentiment extreme tells you the crowd is leaning hard one way; it does not tell you when the tape will turn. Pair it with a real level and a catalyst before it means anything actionable.