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Put/Call OI Ratio

Canonical definition, formula, interpretation, and API reference.

Definition

Total put OI / total call OI. Measures whether positioning is hedging-dominated (>1) or speculation-dominated (<1).

Formula
P/C OI Ratio = Sum(put OI) / Sum(call OI)

Simple ratio across all strikes and expirations.

Inputs
total put OItotal call OI
Output
put_call_oi_ratio
Interpretation
  • >1.0: put-heavy, institutional hedging dominates
  • <1.0: call-heavy, speculative buying
  • Near 1.0: balanced chain, max pain near ATM

Live Example: SPY

Live SPY P/C ratio data temporarily unavailable.

API Reference

Endpoint
GET /v1/maxpain/{symbol}
Tier
Basic+
Response field
put_call_oi_ratio

Why Put/Call OI Ratio Matters for Trading

TL;DR

The put/call OI ratio is a sentiment extreme detector. Extreme highs = capitulation (bounce setups). Extreme lows = euphoria (correction risk).

What it measures
Ratio of total put open interest to total call open interest across the chain.
What it signals
Aggregate positioning bias. Contrarian at extremes; noise in the middle.
Why we measure it
Crowds are wrong at the margin. The ratio surfaces those margins.
Who uses it
Contrarian traders, swing traders, sentiment-model users, retail.

How to read Put/Call OI Ratio

Very high (>1.3)
  • Put-heavy positioning = fear
  • Often marks local bottoms
  • Contrarian long setup
  • Historical mean-reversion edge
Good for: contrarian longs
Very low (<0.6)
  • Call-heavy = euphoria
  • Often marks local tops
  • Contrarian short setup
  • Post-rally exhaustion signal
Good for: contrarian shorts / hedge buys
Typical range (0.7–1.0)
  • Normal sentiment
  • No signal
  • Trade on other factors
  • Background reading
Neutral

Rules of thumb

  • Use absolute extremes, not rolling highs. A 'high' ratio in a bull market may be mid-range historically. Compare to a multi-year distribution.
  • Distinguish OI vs volume ratio. OI ratio is slow/structural. Volume ratio is fast/tactical. Both useful, different use cases.
  • Fades fastest at SPX index level. SPX put/call is the most reliable signal; single stocks noisy.
  • Pair with fear & greed. Ratio extremes + sentiment extremes = higher-conviction contrarian setups.
  • Signal is late, not perfect. Extremes can persist. Contrarian entries need confirmation (price reversal, vol pattern).

Related Concepts

Max Pain
Highest OI Strike
Skew
Dealer Hedging

Learn More

Deep-dive article
Max Pain Guide
API documentation
GET /v1/maxpain/{symbol}
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