What is open interest?
In one line: Open interest is the total number of futures or options contracts that are still open, meaning they haven't been closed, exercised or expired yet.
A simple example
Every futures or options contract has two sides: a buyer and a seller. Open interest counts the contracts that are still alive.
Start the day with open interest at 100 contracts:
- Ana buys 1 new contract and Ben sells 1 new contract. Both are opening. Open interest goes to 101.
- Ana sells her contract to Cara, who is opening a new trade. A contract just changed hands. Open interest stays 101.
- Cara sells to Ben, who is closing his short. Both are closing. Open interest drops to 100.
All three trades add to Volume. Only the first and the third changed open interest.
Volume vs open interest
| Volume | Open interest | |
|---|---|---|
| Counts | Every contract traded today | Contracts still open |
| Resets | Every day | Carries over day to day |
| Shows | How busy the market is | How many positions are still in play |
Why it matters
- Which contract is "live." In futures, open interest moves from the expiring contract to the next one around the roll. The contract with the most open interest is usually where the action is. See Contract rollover.
- Options. A Strike price with big open interest has many contracts riding on it. Many traders like to know where those levels are.
- Context, not a signal. Rising open interest during a move means new positions are being added. Falling open interest means positions are closing. It describes what happened; it doesn't say what comes next.
Our guide on how to read volume covers the other half of the picture.
A common mistake
Reading open interest as bullish or bearish on its own. Every open contract has a buyer and a seller. Big open interest just means lots of people disagree at that price. It doesn't tell you which side is right.
Questions
Where can I see open interest?
Most futures and options platforms show it. The CFTC also publishes the weekly Commitments of Traders report, which breaks open interest down by trader type.
Does forex have open interest?
Spot forex has no central exchange, so there's no single open interest number. Currency futures, like the euro future (6E), do have one.
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