Open Interest

Open interest is the total number of derivative contracts outstanding that have not been settled or closed, counted on one side of the market.

How it works

Open interest counts the contracts that have been opened and not yet closed, expired, or settled. Each contract requires a buyer and a seller, so open interest is measured on one side of the paired positions rather than by adding both legs together. When a new buyer and a new seller create a fresh contract, open interest rises by one. When an existing holder closes against another existing holder, it falls by one. When one party opens and the counterparty closes, the figure stays flat.

In futures, perpetuals, and options markets, open interest is usually reported as a contract count or a notional value. In onchain markets, the same measure is derived from position records held in smart contracts, so the outstanding size can be read directly from the ledger. In prediction markets the equivalent quantity is the value of shares bought on outcomes that have not resolved. Outside finance, the phrase sometimes refers to an unfilled job vacancy, which is a separate usage.

Why it matters

For an institutional reader, open interest indicates how much capital is committed to positions that still carry exposure, which informs liquidity, crowding, and settlement risk assessments. It is distinct from volume, which counts activity over a period rather than standing positions, and the two are often read together, as covered in Open Interest vs Volume: What Each One Tells You. Rising open interest alongside a price move points to new money entering, while falling open interest points to positions being unwound.

Related terms

• Volume
• Notional value
• Perpetual futures
• Funding rate
• Settlement

Frequently asked questions

Does open interest count both the buyer and the seller?

No. Each contract has a buyer and a seller, and open interest counts the paired position once, not twice. Reporting conventions measure one side so the figure reflects the number of outstanding contracts.

How is open interest different from volume?

Volume counts contracts traded during a period and resets each interval. Open interest counts contracts still open at a point in time. A single trade can add volume without changing open interest if it only transfers an existing position.

How is open interest measured onchain?

Onchain markets store position records in smart contracts, so outstanding contract size or notional value can be read directly from the ledger rather than relying on exchange reports.

Allium provides onchain data infrastructure. Companies named in this article may be Allium customers, prospects or commercial counterparties. The authors and other Allium personnel may hold positions in the assets discussed. This article is informational only and is not investment, legal or tax advice. Data and information last reviewed: October 19, 2026.