What Is Open Interest in Options Trading and How to Read It
Open interest tells you something volume can't: whether real money is entering a position, or leaving it. Here's how to read it.
The short version: open interest is the total number of outstanding futures or options contracts that haven’t been closed, exercised, or expired. It’s different from trading volume, and it tells you something volume alone can’t: whether money is flowing into a position, or out of it.
Open interest vs volume — the key difference
Volume counts every trade in a session, whether it opens a new position or closes an old one. Open interest only counts contracts still active. Say you buy a contract, and someone sells it to you. Open interest rises by one, since it’s a brand new position.
Now say that same contract gets sold back and closed. Open interest falls by one. The trade still counts toward volume, but the position no longer exists.
What rising or falling open interest tells you
Rising price, rising open interest. This usually signals fresh buying. New money is entering the market, and the trend has real conviction behind it.
Rising price, falling open interest. This often means short sellers are covering positions, not that new buyers are stepping in. The rally may be less durable than it looks.
Falling price, rising open interest. This usually points to fresh selling, or aggressive short positions being built. It suggests real bearish conviction, not just profit-booking.
Falling price, falling open interest. This typically means long positions are being closed out. It’s often a sign the down-move is running out of steam.
Reading the option chain with open interest
In options trading, open interest is tracked separately for every strike price, for both calls and puts. Traders often watch strikes with unusually high open interest, since these can act as psychological support or resistance levels.
The put-call ratio, built from open interest, is a popular sentiment gauge. A high ratio means more put positions than calls. Some traders read that as a bearish or contrarian signal, though context matters.
Why open interest data has limits
Open interest tells you how many positions exist. It doesn’t tell you who holds them, or why. A large position could be a directional bet. Or it could be part of a hedge, with nothing to do with predicting price direction.
It’s also usually an end-of-day metric, not something to react to tick by tick. Used alongside price and volume, though, it adds real context price alone doesn’t provide.
| Price | Open interest | Likely interpretation |
|---|---|---|
| Rising | Rising | Fresh buying, strong trend |
| Rising | Falling | Short covering, weaker trend |
| Falling | Rising | Fresh selling, strong bearish trend |
| Falling | Falling | Long unwinding, trend losing steam |
Related reading
Frequently asked questions
Is open interest the same as trading volume?
No. Volume counts every trade in a session; open interest counts only contracts still outstanding, whether or not they traded that day.
Where can I check open interest data?
Most exchanges and broker platforms publish live open interest data for futures and options, usually broken down by strike price for options.
What is the put-call ratio?
A ratio of put open interest to call open interest, often used as a rough sentiment indicator, though it shouldn’t be used alone.
Does high open interest at a strike price act as support or resistance?
It can, since large positions may need to be defended or unwound near that level. But it’s a tendency, not a guarantee.
Can open interest predict future price direction on its own?
Not reliably. It’s most useful combined with price action and volume, not as a standalone signal.