What Is Open Interest? Definition & Example

Open interest is the total notional value of all outstanding derivative positions in a market. Unlike volume, which counts every transaction and resets each day, open interest measures what is currently held. It rises when new positions are opened and falls when positions are closed.

The distinction from volume is what makes it useful. High volume with flat open interest means traders are passing positions between each other without net new commitment — churn. High volume with rising open interest means fresh capital is entering and conviction is building.

Read it alongside price and the combination tells a story. Price up, OI up means new longs are driving the move — a genuine trend with capital behind it. Price up, OI down means shorts are covering rather than longs entering, which is a squeeze and tends to exhaust itself. Price down, OI up means new shorts are entering with conviction. Price down, OI down is longs capitulating and closing out.

Open interest is also a leverage gauge for the market as a whole. When OI reaches extremes relative to the asset's market cap, a large amount of leveraged positioning is stacked up, and the market becomes fragile — a modest price move can trigger a liquidation cascade that moves it far further than the original catalyst justified.

Combine it with funding for the fullest picture. High open interest plus extreme funding means a lot of leveraged capital is committed to one side and paying to stay there. Historically that configuration resolves sharply.