Open Interest (OI)
Full form: Open Interest
Open interest, or OI, is the total number of futures or options contracts that are still open, meaning nobody has closed them or let them expire yet. It tells you how many positions exist in the market right now, not how many traded today.
How OI changes
Every contract has two sides, a buyer and a seller, and together they count as one open contract. OI goes up when a new buyer and a new seller create a fresh contract. It goes down when both sides close an existing one. It stays the same when a trader hands an existing contract to someone else, because the contract is still open.
OI is not volume
Volume counts every trade made during the day, whether it opens, closes or passes on a contract. OI counts only what is still open at the end of the day. A very busy day can end with the same OI as the day before.
How traders read OI
Traders often compare OI with price. A rising price with rising OI is commonly read as fresh buying joining the move, and a rising price with falling OI as sellers closing out. These are habits of reading, not rules, and they can be wrong.
In options, a strike with unusually high OI is sometimes watched as a level the market may find hard to cross. That cluster is called an OI wall, and it is a probability at best, never a promise.
Three days of one contract
Day 1: A buys one contract from B. Both are new, so OI is 1.
Day 2: C buys that contract from A. A is closing and C is opening, so OI stays at 1.
Day 3: C sells to B, and both are closing. Nothing remains open, so OI falls to 0.
Common questions
- What does OI mean in the stock market?
- OI means open interest: the number of futures or options contracts that are still open.
- Is high OI good or bad?
- Neither by itself. High OI means many open positions and usually plenty of trading interest. What it signals depends on how the price is moving and on the context.
- What is the difference between OI and volume?
- Volume is how many contracts traded during the day. OI is how many contracts remain open at the end of it.
- Where can I see OI?
- On your broker's option chain and on the exchange's website, which publish OI for each contract.