What is Open Interest (OI)? A Simple Guide for Indian Traders
Open interest (OI) is the total number of derivative contracts that are currently open and not yet settled. It counts outstanding positions, not daily trades. Rising or falling OI shows whether money is flowing into or out of a contract.
Open interest is one of the most useful numbers in derivatives, yet it is often confused with volume. It tells you how much commitment sits behind a contract.
Reading OI helps you spot support, resistance and the strength of a move. What follows is a no-nonsense guide for Indian traders. You can view OI data on Stockk.
Key Takeaways
- OI is the number of open, unsettled contracts.
- It counts positions, not daily trades.
- Heavy call OI marks resistance; heavy put OI marks support.
- Rising OI shows fresh money entering.
- OI is read alongside price for buildup signals.
How is open interest different from volume?
Volume counts how many contracts traded during a session, while open interest counts how many positions remain open at the end. Volume can be high even if OI is flat, when traders open and close within the day. OI shows the standing commitment in a contract.
| Feature | Volume | Open interest |
|---|---|---|
| Counts | Trades in a session | Open positions |
| Resets daily | Yes | No, it carries over |
| Shows | Activity | Commitment |
How do traders read open interest?
Rising OI with rising price suggests fresh buying and a strengthening trend, while rising OI with falling price suggests fresh selling. Concentrations of OI at specific strikes mark likely support and resistance.
Picture this: a NIFTY 22,800 call has very high open interest. Heavy call OI at that strike often marks a resistance zone, while heavy put OI at a lower strike marks a support zone.
OI and price together
- Price up, OI up: fresh buying, bullish
- Price down, OI up: fresh selling, bearish
- Price up, OI down: short covering
- Price down, OI down: long unwinding
These four combinations are the basis of buildup analysis, covered in related terms.
Why OI strikes act as support and resistance
Large OI reflects many positions that traders defend. When a lot of call writers are positioned at a strike, they have an interest in price staying below it, which can act as resistance. The same logic makes heavy put OI act as support. This is why the option chain's OI distribution is watched so closely.
Curious to try F&O with full options data yourself? Head to Stockk, open a quick demat account, and use the Knowledge Center whenever you need a refresher.
Futures and Options are leveraged products and carry a high risk of loss that can be more than the money you put in. This article is only for learning and is not a recommendation to trade in derivatives.
Frequently Asked Questions
What does high open interest indicate?
It signals many open positions and strong participation at that contract or strike. Heavy OI strikes often act as support or resistance, reflecting standing conviction.
How is OI different from volume?
Volume measures contracts traded in a session, while OI measures positions still open. They answer different questions, and together they give a fuller picture.
Does rising OI mean a strong trend?
Rising OI with a rising price suggests fresh buying and trend strength. The combination matters, not OI alone; falling OI suggests positions closing.
Why do OI strikes act as support or resistance?
Large OI reflects many positions that traders defend, concentrating order flow at those strikes, which creates support and resistance zones visible in the option chain.
How do I use OI with price?
Read OI change alongside price change to judge whether new positions are bullish or bearish, which is buildup analysis.
Investments in securities market are subject to market risks. This article is for educational purposes only and does not constitute investment advice.
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