Open interest (OI) is the number of futures or options contracts that are open — created and not yet closed or expired. It measures how much money is positioned, not how much changed hands today (that is volume).
- A new buyer and a new seller opening positions → OI rises.
- Both closing existing positions → OI falls.
- One side passing a position to someone else → OI unchanged.
Reading change in OI with price
The classic way to read futures OI is to combine it with the price move:
| Price | OI | Usual reading |
|---|---|---|
| Up | Up | Long build-up |
| Down | Up | Short build-up |
| Up | Down | Short covering |
| Down | Down | Long unwinding |
OI in the option chain
In options, traders watch where OI is concentrated:
- Heavy call OI at a strike is often read as a resistance level — option writers have sold calls there.
- Heavy put OI at a strike is often read as support — writers have sold puts there.
- A shift of the largest OI to a new strike during the day is often read as those levels moving.
These are readings of positioning, not guarantees. Large OI can be broken, and when it is, the move can speed up as writers adjust.
Seeing it live
The NEOGreeks terminal shows OI and change in OI across the chain for NIFTY, BANKNIFTY, SENSEX and BANKEX, the nearest call and put walls, and — in Range Watch — a record of when those levels broke during the day. See what's in it.