What Is Open Interest? 2026 Crypto Derivatives Basics

#What is Open Interest?

Open Interest refers to the total number of outstanding contracts in a derivatives market, reflecting the current size of open positions. Unlike completed trading volume, open interest measures the stock of market exposure, not the flow.

Take BTC perpetual contracts as an example. If a trading platform currently has 100,000 open contracts, the open interest is 100,000 contracts. Each contract represents one buyer and one seller with unsettled obligations, but open interest counts it only once.

The concept of open interest applies to futures, options, and other derivatives, and is one of the fundamental indicators for measuring market depth. To learn more about derivatives, you can refer to the Introduction to Cryptocurrency Derivatives.

#What is the difference between open interest and trading volume?

Trading volume is the number of contracts that have been traded, a flow indicator; open interest is the total number of currently open contracts, a stock indicator. A simple analogy: trading volume is like the total foot traffic entering and exiting a shopping mall today, while open interest is like the number of people currently inside the mall.

Dimension	Trading Volume	Open Interest
Nature	Flow (already occurred)	Stock (current state)
Change	Accumulates over time	Increases/decreases with opening and closing positions
Example	50,000 contracts traded in a day	20,000 contracts currently open

Trading volume can be very high in a day while open interest remains unchanged, because a large portion of the volume is just turnover — old contracts are closed and new contracts are opened, so open interest does not change. This indicates that the market is active but no net new capital has entered.

#How does open interest change with opening and closing positions?

Changes in open interest depend on the combination of opening and closing positions. The bullet list below explains four common scenarios:

• Both sides open new positions: A new buyer and a new seller open positions at the same time, open interest +1.
• Both sides close positions: The original buyer and original seller close positions at the same time, open interest -1.
• One side closes and the other opens: Open interest remains unchanged (turnover).
• Both sides open and close partially: Open interest changes by the net number of opened contracts.

Each new opening creates both a buyer and a seller, but open interest counts only one contract because one contract corresponds to a pair of long and short positions. For example, if open interest in a contract increases from 100,000 to 105,000 contracts, it means 5,000 contracts were net opened, indicating new capital entering the market.

To learn more about trading volume indicators, you can refer to the detailed guide on trading volume.

#Why is open interest important? Common misunderstandings and risks

Open interest reflects market activity and the level of capital participation. Rising open interest often accompanies trend continuation, while a decline may signal a weakening trend. However, rising open interest does not mean prices will necessarily rise; it only means market exposure has increased. The direction must be judged together with price and volume.

When open interest increases, prices rise, and volume expands, it usually indicates a healthy uptrend; when open interest increases but prices fall and volume expands, it may be dominated by short sellers. This judgment requires experience and is also affected by market manipulation and other factors, so it cannot be applied mechanically.

A common misunderstanding is to focus only on open interest while ignoring price and volume. Outstanding contracts are synonymous with open interest; derivatives include futures, options, etc. Additionally, derivatives trading carries higher risks, and open interest analysis cannot replace risk management. If your account triggers liquidation, you need to understand the liquidation price. This article does not constitute investment advice.

This article is compiled by MSX Learn for educational purposes only.

#Frequently Asked Questions (FAQ)

What is Open Interest? Open Interest is the total number of outstanding contracts in a derivatives market, reflecting the overall market exposure, and is a different concept from completed trading volume.

What is the difference between Open Interest and trading volume? Trading volume is the number of contracts that have been traded, while open interest is the total number of currently open contracts. Volume is like foot traffic, open interest is like the number of people inside.

Does rising Open Interest mean prices will definitely rise? Not necessarily. Rising open interest only indicates increased market exposure; the direction is determined by both price and volume. For example, if open interest rises but prices fall, it may indicate that shorts are actively opening positions, potentially leading to a continuation of the downtrend; conversely, if open interest and prices rise together, the uptrend is stronger. Therefore, it should be interpreted in conjunction with the overall trend.

How to judge capital inflows and outflows from changes in Open Interest? Opening positions increases open interest, closing positions decreases it, and turnover leaves it unchanged. A sustained increase in open interest generally means new capital is entering, while a decline may indicate capital exiting, but this is not absolute and should be combined with price and other indicators.