Open Interest: What It Measures in NSE F&O
Open interest (OI) is the number of outstanding futures and options contracts. OI change alongside price shows whether positions are being built, covered or unwound.
Last updated: September 2026 · Reviewed quarterly · Data: live NSE derivatives feeds, 09:15–15:30 IST
What open interest measures
Outstanding positioning per strike and expiry — not direction by itself. Meaning comes from OI change × price change × volume read together.
How it is calculated
- Inputs: live NSE derivatives OI, OI change, traded volume and price per contract.
- Aggregation: per-strike and per-expiry totals; change versus prior session and intraday baselines.
- Refresh: continuously during market hours. See methodology §6a.
What the numbers mean
- Rising OI + rising price: long build-up (fresh buying).
- Rising OI + falling price: short build-up (fresh selling).
- Falling OI + price move: position covering or unwinding — weaker conviction than fresh build-up.
Limitations
- OI reflects hedging as well as direction; writers and hedgers leave the same footprints as directional traders.
- Expiry-day rolls and illiquid strikes distort readings; check volume before concluding.
- Informational analytics, not investment advice. See disclaimer.
Example
Nifty futures add 8% OI while price falls 0.6% on heavy volume — short build-up. Traders confirm regime on Index Pulse rather than fading the flow.
Related metrics
Open Interest FAQs
What is open interest?
Outstanding futures/options contracts per strike and expiry. OI change with price and volume indicates build-up, covering or unwinding.
Does rising OI always mean bullish?
No. Rising OI with falling price indicates short build-up. Direction comes from the combination, not OI alone.
Why does OI behave oddly on expiry?
Rolls and settlement flows move OI without directional meaning. Interpret expiry sessions separately.