Open interest (OI)
Open interest (OI) is the number of option or futures contracts outstanding at a stated time, each counted once although it has a long and a short side. It is published once a day after the close, it does not identify who holds either side, and it differs from volume, which counts trading over an interval.
Senzoukria · Glossary · Updated September 2026
Open interest versus volume
A contract can change hands many times in a session, so volume can exceed prior open interest without every transaction opening a new position. Volume above open interest signals high turnover relative to the last snapshot, not proof of new positioning. The clearing organisation's reports distinguish the two, and a dashboard should as well.
| Measure | What it counts | When it updates |
|---|---|---|
| Volume | Contracts traded during an interval | Continuously, with each trade |
| Open interest | Contracts outstanding at a point in time | Once daily, after the close |
What OI cannot tell you
- Who holds the long side and who holds the short side. Every open contract has both, and the count says nothing about either.
- Whether today's trades opened or closed positions; that only appears in the next day's figure.
- Whether a call was bought or sold, or belongs to a spread or a hedge.
- Intraday changes. Gamma and delta move with spot and time during the day, but open interest stays at its published value until the next update.
Its role in gamma exposure
Dealer GEX models use open interest as the position size at each strike, multiply by gamma and a contract multiplier, and apply a sign from a positioning assumption. Because OI does not name holders, that sign is a convention rather than a measurement. Because OI is a once-daily figure, a GEX level computed at noon uses positions as of the previous close, repriced with the current spot and volatility. A ratio such as volume divided by open interest is unstable when the denominator is small, and a missing open-interest value must never be treated as zero.
In Senzoukria
The GEX module takes open interest from the configured options chain as published. On the Surface page, Open interest is one of the Value plotted choices, and the page's note states that open interest and implied volatility come from the chain while gamma, vanna and charm are model output. The Net GEX by strike page shows an OI readout of calls and puts per strike, and the regime panel displays a Put / call OI figure. The Calculation assumptions panel carries a Data freshness section with the chain snapshot time and a note that open interest is published once a day after the close, so intraday gamma moves with spot and time, not with positions taken today. The Options flow view on this site is a separate observation of transactions, not a substitute for OI.
Common mistakes
- Reading rising open interest at a call strike as bullish; the contracts have a seller too.
- Using yesterday's open interest as if it described positions opened this morning.
- Filling a missing OI value with zero and letting it silently change a GEX total or a wall selection.
Related
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Frequently asked questions
- Why does open interest only update once a day?
- Because it is computed by the clearing process after each session, once opening and closing transactions have been netted. Volume is reported trade by trade during the day, which is why an intraday options flow feed and an open-interest snapshot describe different things and should be timestamped separately.
- Can volume exceed open interest?
- Yes. Contracts can turn over repeatedly within a session, so daily volume can be larger than the number of contracts outstanding. That indicates high turnover relative to the prior snapshot, not that every trade opened a new position; the net effect only shows in the next published open-interest figure.
- Does high open interest at a strike mean dealers are short gamma there?
- No. Open interest counts contracts without naming the holders, so the sign of dealer gamma at that strike is an assumption applied by the model. Senzoukria exposes that assumption in its Dealer positioning setting; reversing it flips the sign at every strike while the open-interest numbers stay the same.