Open interest (OI) explained, with examples
Updated 2026-10-24 · 6 min read
Open interest, or OI, tells you how many futures or options contracts are still open, meaning they have been created and not yet closed or settled. Watching how it changes helps traders understand whether money is flowing into a move or out of it.
Open interest vs volume
Volume counts every contract traded during the day. Open interest counts contracts still outstanding at the end of it. If a trader buys a contract and sells it the same day, that adds to volume but leaves open interest unchanged.
How open interest changes
- A new buyer and a new seller create a contract: OI rises by one.
- One side closes and passes the position to a new participant: OI is unchanged.
- Both sides close their positions: OI falls by one.
Reading price and OI together
| Price | Open interest | Common reading |
|---|---|---|
| Rising | Rising | Long build-up: new buying behind the move |
| Falling | Rising | Short build-up: new selling behind the fall |
| Rising | Falling | Short covering: sellers closing positions |
| Falling | Falling | Long unwinding: buyers exiting |
These labels describe what usually happens. They are not guarantees, and the same pattern can mean different things in different market conditions.
Strike-wise open interest
In index options, traders look at which strike prices have the most open interest. Strikes with very large call OI are often read as zones where sellers expect the market to struggle, and strikes with large put OI as zones where they expect it to hold. These zones shift as positions change, especially near expiry.
Limits of OI
- It does not tell you who is buying and who is selling, or whether a position is a hedge.
- It changes sharply around expiry and rollovers.
- It is best read together with price, the put-call ratio and volatility.
Open interest on TradeIntel AI
TradeIntel AI turns options data into a plain-language positioning summary for Nifty and Bank Nifty: put-heavy, balanced or call-heavy, with activity and volatility context. It does not give strike-level buy or sell calls.