Open interest (OI)
Open interest (OI) is the total number of futures or options contracts that are open and not yet closed. It shows how much money sits in positions, not their direction.
How it works
Every contract has two sides: a buyer (long) and a seller (short). So one trade adds one contract to OI, not two, and there are always exactly as many longs as shorts. OI rises when new positions open and falls when positions are closed or liquidated.
OI is not volume. Volume counts every trade in a period, including closes. OI is a snapshot of what is still open right now. It is shown in contracts, coins or dollars; a rise in dollar OI can simply come from a higher price.
Traders read OI together with price and funding. Price and OI both rising means new positions are coming in. Price rising while OI falls is often shorts closing, not fresh buying. Very high OI with skewed funding means a lot of leverage and a risk of cascading liquidations either way.
BTC futures OI is 10,000 BTC. Trader A opens a 5 BTC long and trader B opens a 5 BTC short against it. OI becomes 10,005 BTC: one trade, plus 5 contracts.
In a day ETH rose 3% while OI fell 8%. That means the rally came mostly from shorts closing (forced buying), not new buyers. Such a move can run out of steam quickly.
A common mistake is treating rising OI as a bullish signal. OI says nothing about direction: every new long has a new short on the other side. Read OI only together with price, funding and volume, and remember that high OI mainly means lots of leverage and a risk of sharp liquidations.
Questions and answers
What is open interest in simple terms?
It is how many futures or options contracts are currently open and not yet closed. The higher it is, the more money and leverage are in the market.
What is the difference between open interest and volume?
Volume counts all trades over a period, including position closes. OI shows how many positions remain open at a given moment.
Is rising open interest bullish or bearish?
Neither by itself. It means new positions are opening, but it does not tell you where price will go. Read it with price and funding.
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Updated: 2026-10-19