What is open interest, boiled down to a single number?
Open interest (OI) is the total number of derivative contracts (futures or perpetuals) that are open right now and that nobody has closed yet. It is not trading volume. Volume counts how much changed hands during the day. OI counts how many positions are alive at this moment.
To be concrete: our own live figure for BTC today, read at 09:30, came in at 2.7bn USD (source: syndicate). That number means the combined value of the open BTC contracts we track was 2.7 billion dollars at that moment. On its own it says nothing about direction. It only gets interesting when you read it together with price and with its own change over time.
You can find the detailed definition in our open interest glossary entry.
Why is OI not the same as volume?
Picture two traders. One opens a long, the other opens a short on the opposite side. One new contract has been created, so OI goes up by one. Volume goes up too. So far they behave the same.
Now the first trader sells their position to a third trader, who takes it over. Volume rises again (a trade happened), but OI does not change, because the contract merely changed owner; no new one was created and none disappeared. OI only falls once both sides agree to close the position.
That is why a simple rule holds: volume measures activity, OI measures how much money stays in play.
How do you read OI together with price?
This is the whole core of the lesson. Price and OI have four possible combinations, and each one tells a different story about whether new money is flowing in or positions are being closed.
| Price | Open interest | Most common reading |
|---|---|---|
| rising | rising | new money opening longs, the move is backed by fresh capital |
| rising | falling | shorts closing positions (short covering), the move is driven by closing, not new buyers |
| falling | rising | new money opening shorts, the drop is backed by fresh capital |
| falling | falling | longs closing positions, money is flowing out of the market, the move is weakening |
Notice the difference between the rows. When price rises and OI rises, new capital is entering the market and opening longs. When price rises but OI is falling, the price is often driven by short covering, meaning people who bet on a decline are buying back to get rid of a losing position. The result on the chart looks similar (price up), but under the surface it is a completely different situation.
Let's show it on our 2.7bn USD
Take our value of 2.7bn USD read at 09:30. On its own it is just a snapshot of a single moment. It only becomes useful in comparison.
Let's imagine two scenarios for the afternoon:
- BTC price rises by 15:00 and OI jumps from 2.7 to 3.1bn USD. Reading: roughly 0.4bn USD of new capital flowed in and is opening positions. The move has new money underneath it.
- BTC price rises just the same by 15:00, but OI falls from 2.7 to 2.4bn USD. Reading: the price is probably driven by position closing, not by new capital. Same price move, different engine.
Important: this is a description of the mechanics, not a forecast. OI will not tell you what comes next. It tells you what feeds the current move.
Where are the limits of what OI reveals?
OI has its blind spots, and it is only fair to name them.
- It does not tell you who is on which side. Rising OI with rising price is usually read as opening longs, but on the other side of every long there is a short. It is a probable reading, not proof.
- The dollar value fluctuates with price. When you measure OI in USD (like our 2.7bn), part of the change may simply be because the price of the underlying moved, not because contracts were added. That is why OI is sometimes tracked in the number of contracts or in BTC instead.
- It depends on what you count. Our number covers the sources we track via syndicate, not necessarily the entire market. Different providers arrive at slightly different numbers depending on which exchanges they include.
- A change in OI alone gives no direction. Without reading it together with price, a rise in OI is neutral; it can mean new longs just as easily as new shorts.
What can you do now and what remains uncertain?
After this lesson you should be able to:
- tell open interest apart from volume (how many positions are alive vs. how much changed hands),
- read the four price/OI combinations and say whether the move is driven by new capital or by position closing,
- take a specific number (say our 2.7bn USD from 09:30) and compare it with a later reading, so you see the flow, not just a snapshot.
What remains uncertain: OI will never tell you with certainty who is on which side of a trade, nor what will happen next. It is a tool for reading what is happening right now, not a crystal ball. And the dollar value always carries within it the price movement of the underlying too, so quick changes are best verified in the number of contracts as well.