# What is open interest in options?

Canonical: https://halfonadouble.com/learn/open-interest
Data through: 2026-10-16 close
Publisher: Half on a Double

**Open interest in options is the number of contracts still outstanding at a
reporting snapshot.** Volume counts contracts traded during a session. Open
interest counts each buyer-and-seller pair once; it is not a count of shares
or separate investors. A trade reduces OI when both counterparties close
existing positions; exercise and expiration can also remove contracts.
[OIC explains the distinction and OCC's role in
calculating it](https://www.optionseducation.org/news/open-interest-why-it-matters).

## Open interest vs volume

| Question | Open interest | Volume |
| --- | --- | --- |
| What does it measure? | Contracts remaining open | Contracts traded in a session |
| When does it update? | After daily clearing | During the trading session |
| Does another trade always increase it? | No; positions can open, close or transfer | Yes; another contract traded adds one |
| Does it reveal bullish or bearish intent? | No | No, by itself |

A single option series specifies a call or put, strike and expiration.
Its OI differs from a ticker's **total OI**, which combines many series.
Compare figures with the same scope and date.

OCC determines updated OI after matching the day's opening and closing
transactions. During trading, a quote can therefore pair current-session
volume with the previous cleared OI. Check the timestamp rather than treating
them as simultaneous measurements. [OIC's reporting
explanation](https://www.optionseducation.org/referencelibrary/faq/general-information).

## Worked example: opening, closing and transferring contracts

This invented example uses one option series. It begins the day with **100
open contracts** and assumes no exercises, expirations or other adjustments.
The running OI below explains the arithmetic; it is not an intraday OI feed.

| Trading during the day | Added volume | OI change | Running OI |
| --- | ---: | ---: | ---: |
| A buyer opens 30 contracts against a seller also opening | 30 | +30 | 130 |
| A holder sells 40 contracts to close; the buyer opens | 40 | 0 | 130 |
| A short holder buys 10 contracts to close; the seller opens | 10 | 0 | 130 |
| A holder sells 10 contracts to close; the short holder buys to close | 10 | −10 | 120 |

The session finishes with **90 contracts of volume** and **120 contracts of
OI**: `100 + 30 − 10 = 120`. Fifty contracts changed holders without changing
OI. The four opening/closing combinations follow [OIC's transaction
examples](https://www.optionseducation.org/news/open-interest-why-it-matters).

Now imagine a second session: 25 contracts open and 25 close. Volume is 50,
but OI remains 120. **Unchanged OI does not mean nothing happened**, or that
every transaction was a transfer. Offsetting increases and decreases can
produce the same closing number.

## Common questions

### Can volume be higher than open interest?

Yes. The same position can change hands repeatedly. In another synthetic
example, ten existing contracts transfer five times: that adds 50 volume
while leaving OI at ten. Comparing today's volume with yesterday's OI does
not reveal which individual trades opened or closed positions.

### Is rising call open interest bullish?

It establishes that more calls remain outstanding, not who bought or sold
them or how they fit into a wider portfolio. Each contract has opposing
sides. OIC explicitly cautions that increasing OI alone establishes neither
a bullish nor bearish outlook. [OIC's open-interest
FAQ](https://www.optionseducation.org/referencelibrary/faq/general-information).

### Does high open interest guarantee liquidity?

No. Check current bid/ask spreads and quoted size for the specific contract.
A large outstanding count does not guarantee an executable price or enough
size for an order. [OIC's liquidity
FAQ](https://www.optionseducation.org/referencelibrary/faq/general-information).

### Does open interest reveal dealer hedging?

No. A public contract count does not identify dealers' net inventory or
offsetting positions. [Cboe's analysis of market-maker
gamma](https://www.cboe.com/insights/posts/volatility-insights-evaluating-the-market-impact-of-spx-0-dte-options/)
explains why net positions and offsets matter. The [gamma exposure
guide](/learn/gamma-exposure) distinguishes modeled positioning from observed
dealer holdings.

## Read current open-interest data

Open the [SPY options snapshot](/stock/SPY) or the [GME options
snapshot](/stock/GME). Start with the displayed data date, total open interest
and change versus the previous session. Those are ticker-wide snapshots;
they are not the single-series examples above. Where historical comparisons
are available, use their stated periods when comparing changes.

For broader comparisons:

- [Most open interest](/screens/most-open-interest) compares the largest
  published ticker totals.
- [Open interest surge](/screens/open-interest-surge) compares five-session
  growth.
- [Unusual open interest accumulation](/screens/unusual-open-interest-accumulation)
  highlights increases that are unusual for that ticker's history.

These screens describe outstanding contracts. They do not identify a buyer's
intent or recommend a trade. Read the [methodology and data
limitations](/methodology) alongside the values.

## Related

[Put/call ratio](/learn/put-call-ratio) · [Gamma exposure](/learn/gamma-exposure)
· [Max pain](/learn/max-pain) · [All learning guides](/learn)