What is Open Interest?
Open Interest is the total number of outstanding perpetual or futures contracts that remain open and unsettled at a given moment. Each contract requires one long and one short, so open interest measures how much capital is currently committed to a market — not how much has traded.
Open interest (OI) counts every derivative contract that is currently open — positions that have been entered but not yet closed, offset, or settled. Because every perpetual futures position pairs one long with one short, a single unit of open interest represents both sides of a live bet. When a new buyer and a new seller open a position against each other, OI rises by one contract; when both sides close, it falls by one. If an existing holder simply passes their position to a new trader, OI stays flat even though volume ticks up.
OI is usually reported in two ways: in contracts (or base units like BTC) and in notional USD (contracts multiplied by mark price). Notional OI is the figure most screeners display, because it lets you compare a $12B BTC market against a $400M SOL market on the same scale. Rising notional OI can come from more contracts, a higher price, or both — so it pays to check which is moving.
The core interpretation rule combines OI with price direction. Rising OI with rising price means new money is funding longs — a bullish, well-supported move. Rising OI with falling price means new shorts are pressing — bearish conviction. Falling OI means positions are being closed regardless of price direction, signalling that a move is running out of fuel rather than gaining fresh participants.
For funding-rate arbitrageurs, OI is an early-warning signal that most traders overlook. When OI climbs sharply and the market becomes crowded on one side, the perpetual's funding rate tends to spike as the dominant side pays to keep its positions open. A delta-neutral arb desk watching OI build on a single venue can anticipate an incoming funding spike and position the short-funding leg before the rate widens — turning crowd behaviour into a carry opportunity. Thin OI, by contrast, warns that a headline funding rate may be fragile: little capital is anchoring it, and slippage on entry can eat the edge.
Always read OI alongside trading volume and liquidity. High OI with low volume signals a market where capital is parked but not actively churning — stable funding, but harder to exit at size. High volume with flat OI signals churn without commitment. On this screener, OI floors are used to filter phantom listings: a market with dust OI and a screaming funding rate is almost never a real, tradeable arbitrage.
How it's calculated
Open Interest (contracts) = total long contracts = total short contracts Notional OI (USD) = Open Interest (contracts) x Contract Size x Mark Price Delta OI = New positions opened - Positions closed
Longs and shorts are always equal, so OI counts each matched pair once, not twice.
Worked example: counting contracts
- •Start of day: BTC perp open interest = 0 contracts.
- •Trader A opens a 10 BTC long; Trader B takes the other side with a 10 BTC short.
- •New positions created -> OI rises to 10 BTC (one matched pair).
- •Trader C buys 4 BTC from Trader A (A closes part of the long).
- •Position only changes hands, no new contract -> OI stays 10 BTC, but volume += 4 BTC.
- •Notional OI = 10 BTC x $68,000 mark price = $680,000.
- •Later, A and B both fully close -> OI falls back toward 0.
- •Read-through: volume was 14 BTC that day, yet peak OI was only 10 BTC — volume measures activity, OI measures commitment.
Open Interest vs Trading Volume
| Dimension | Open Interest | Trading Volume |
|---|---|---|
| Measures | Contracts currently open | Contracts traded in a period |
| Time frame | Snapshot (right now) | Cumulative (per hour/day) |
| Increases when | New positions are opened | Any trade executes |
| Resets | Never — it is a live total | Each new period (e.g. daily) |
| Signals | Commitment / capital at risk | Activity / liquidity |
| Funding-arb use | Predicts funding-rate spikes | Estimates exit slippage |
FAQ
Is higher open interest better?
Higher OI means more capital is committed and usually deeper liquidity, which is good for entering and exiting at size. But higher is not automatically better — very crowded OI on one side often precedes a funding spike or a sharp liquidation cascade. For arbitrageurs, adequate OI matters more than maximum OI: enough depth to trade without slippage, but not so lopsided that funding becomes unstable.
Is open interest bullish or bearish?
Open interest alone is directionless — it must be read with price. Rising OI plus rising price is bullish (new longs funding the move); rising OI plus falling price is bearish (new shorts pressing). Falling OI in either direction signals the current trend is losing participants rather than gaining conviction.
What happens when open interest increases?
Increasing OI means new contracts are being created — fresh money is entering the market rather than existing positions simply changing hands. This typically confirms the prevailing price move and deepens liquidity. If the increase is heavily one-sided, expect the funding rate to move against the crowded side as they pay to hold their positions.
Open interest vs trading volume — what is the difference?
Volume counts how many contracts traded during a period and resets each period; open interest counts how many contracts remain open right now and carries over continuously. A trade can add volume without changing OI if a position merely changes hands. Volume measures activity and helps estimate slippage; OI measures committed capital and helps anticipate funding-rate behaviour.
See open interest live across 36 exchanges.
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