Strike pinning (pinning to a strike)
Strike pinning is the tendency, observed on some expiration days, for an underlying to close at or very near a strike with large open interest. The usual explanation is the hedging of long-gamma option books, which sell above the strike and buy below it; the effect is neither systematic nor guaranteed.
Senzoukria · Glossary · Updated September 2026
At a glance
- When
- Expiration days, mostly the final hours
- Proposed mechanism
- Delta hedging of long-gamma positions at a large strike
- Not to confuse with
- Pin risk (assignment uncertainty for option sellers)
The mechanism
Near expiry, the gamma of an at-the-money option becomes very large: the delta of a strike expiring today swings between almost 0 and almost 1 over a small price range. A holder of a large long-gamma position who re-hedges to stay delta neutral sells the underlying when price rises above the strike and buys when it falls below. If that hedging is large relative to other flows, it pulls price back toward the strike. With the index at 500 and 15% implied volatility, the gamma of the 500 strike is about 0.20 per point with a full session left and about 0.50 with one hour left, which is how quickly the effect can intensify.
When pinning is more or less plausible
- More plausible: large open interest concentrated at one strike close to spot, a quiet news day, and a book that is net long gamma at that strike.
- Less plausible: heavy directional flow, macro releases during the session, or a book that is short gamma at the strike, which would push price away instead.
- Cash-settled index options settled at the open, such as standard monthly SPX series, lose their gamma before the session begins, so they cannot pin the afternoon close.
- Academic studies of US single-stock options have reported clustering of closing prices near strikes on expiration dates; the size of the effect varies and is not a trading rule.
How to test it
Record before the session the strikes with the largest open interest or modelled gamma near spot, then measure the closing distance to the nearest such strike across many expiration days, and compare with non-expiration days and with strikes chosen at random. Include the days the pin failed. A handful of memorable pins proves nothing, and a strike that happens to be near spot will often be near the close by chance alone.
In Senzoukria
The GEX module can isolate options expiring today through the 0DTE only setting of the Calculation assumptions panel, which shows where same-day gamma sits relative to spot. The Levels history page records the call wall, put wall and flip once a minute, and the Gamma through the session view shows exposure by price over time, which is where a strike absorbing more and more exposure through the afternoon can be observed. None of these views predicts a pin; they record the conditions under which one is discussed.
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Frequently asked questions
- Is pinning the same as max pain?
- No. Pinning is about hedging flows near one heavily traded strike. Max pain is a calculation of the settlement price that minimises the payout to option holders across all strikes. They can point to the same strike but rest on different reasoning, and neither is guaranteed.
- Does pinning work on futures?
- Futures are not pinned by their own options in the same way unless the futures options carry large gamma at a strike. On ES and NQ, any pinning discussed usually refers to SPX, SPY, NDX or QQQ strikes transposed to the futures price, which adds a basis to the level.