Open interest and price: long buildup, short buildup, short covering and long unwinding

Price alone does not tell you whether a move is supported by new positions. Adding open interest to the picture gives four classic readings that traders use for futures and options.

The four combinations

• Price up, open interest up: long buildup. New buyers are entering and positions are being added on the long side.
• Price down, open interest up: short buildup. New sellers are entering as the price falls.
• Price up, open interest down: short covering. Existing short positions are being closed, which pushes the price up.
• Price down, open interest down: long unwinding. Existing long positions are being closed as the price falls.

Why open interest matters

Open interest counts contracts that are still open. When it rises, new money is entering the market. When it falls, positions are leaving. A price move with rising open interest is often seen as having more participation than a move with falling open interest.

How to apply it to options

In options, each strike has its own change in OI. A large rise in put OI at a strike with the price rising is read by some as put writers adding support. A large rise in call OI at a strike is read by some as call writers adding resistance. Both are interpretations of who the writers are, which the data does not confirm.

Limits

• Open interest does not say who the buyer or seller is. Each contract has both.
• An increase in OI can be hedging or spreads, not directional bets.
• Rollovers near expiry move open interest from the current series to the next one, so OI changes around expiry are hard to interpret.
• A single day is a small sample. Look at several sessions.

A worked example

Say a stock's futures closed 2% higher and open interest rose 8% compared with the previous session. Price up and open interest up is a long buildup: new long positions were added on the day. If the same stock rose 2% but open interest fell 8%, that is short covering: the price rise came from shorts closing, not from fresh buying, which some traders treat as a weaker move.

Try the same exercise for one stock over five sessions. If the readings keep changing from one day to the next, the market is not showing a clear trend in positioning, and that is useful to know too.

Reading Tradingraph's OI chart

The OI Bar Chart shows total open interest and the change in open interest for calls and puts across strikes, from NSE's end-of-day file. It highlights where positions were added or removed on the session.

This page is for information and education only and is not trading advice.