What is open interest in options? Open interest vs volume
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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.
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.
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.
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.
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.
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 explains why net positions and offsets matter. The gamma exposure guide distinguishes modeled positioning from observed dealer holdings.
Read current open-interest data
Open the SPY options snapshot or the GME options snapshot. 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 compares the largest published ticker totals.
- Open interest surge compares five-session growth.
- 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 alongside the values.
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