Open interest is the most quoted number in Indian options and the most misread. Every second Telegram message says "heavy OI at 77000, big resistance". Most of the people forwarding that line cannot tell you what the number actually counts.
So let us fix that from the ground up, using SENSEX weekly options — BSE, Thursday expiry, lot size 20, strikes every 100 points.
Open interest is the number of contracts currently open and unsettled in one specific option — one strike, one expiry, one type. Not today's activity. Not cumulative history. Just: how many live positions exist in that contract right now.
Every option contract has two sides. Someone bought it, someone sold it. One open contract equals one buyer and one seller, and it counts as 1 in open interest, not 2.
Here is the part that trips people up. Whether OI moves depends on what kind of transaction happened:
Volume counts every one of those as a trade. Open interest only counts whether contracts were created or destroyed. That is the entire difference, and it is why the two numbers tell you different things.
Picture tickets to a match. Volume is every ticket transaction today, including resales. Open interest is how many tickets are held by someone planning to walk in on match day.
If tickets keep being resold between the same crowd, volume is huge and open interest does not move — no new people are coming. If the stadium keeps issuing fresh tickets, open interest climbs, and that means genuinely more people have committed to showing up.
Now add price. If ticket prices are rising and fresh tickets are being issued, demand is real and new money is arriving. If prices are rising while the total ticket count shrinks, what you are watching is people who were short the match scrambling to buy their way out — not fresh enthusiasm.
This is the specific combination in the title, so let us be precise about it.
When the price of a contract rises and open interest rises at the same time, new contracts are being created at higher prices. Fresh buyers are willing to pay more, and fresh sellers are willing to take the other side at those levels. New money is entering, not just changing seats.
In the standard reading this is called a long buildup, and it is treated as the combination where a move has fresh participation behind it rather than being an unwind of old positions.
| Price | Open interest | What it describes |
|---|---|---|
| Up | Up | Long buildup — new positions created into strength |
| Up | Down | Short covering — old shorts closing, not new demand |
| Down | Up | Short buildup — new positions created into weakness |
| Down | Down | Long unwinding — old longs exiting |
This table is descriptive, not predictive. It tells you what kind of activity produced a move that has already happened. It does not tell you what comes next.
Expiry decay distorts everything. As Thursday approaches, out-of-the-money options bleed premium regardless of participation. A strike whose price falls while OI rises may simply be a market that is running out of days, not one taking a directional stance.
Exchange OI is an end-of-day figure. The official number is computed after the close. Intraday "live OI" on your broker's screen is an estimate. Treat intraday spikes with more suspicion than you treat the settled number.
OI is per contract, and there are hundreds. With a 100-point strike step and both CE and PE across multiple expiries, "SENSEX OI" is not one number. Always name the strike, the expiry, and the type.
You cannot see who is on which side. A huge OI figure at 77000 CE could be institutions writing calls, or a hedge leg against a futures position, or an arbitrage book with no directional view at all. The number is a count, not a motive.
Open interest is a good question to ask about a move. It is a poor answer to the question of what to do next.