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Glossary

What Is Open Interest? OI vs Volume Explained

Open interest, or OI, is the number of outstanding derivatives contracts that have not been closed or settled at a point in time. Volume counts contracts traded during a period instead. Every outstanding contract has both a long and a short side, so rising OI alone is not a bullish or bearish forecast.

How a trade changes open interest

Buyer and seller intentTypical OI effect
Both create new positionsIncreases
Both close existing positionsDecreases
One opens while the other closesUnchanged

Each transaction still contributes to volume. This explains why volume and OI answer different questions.

Interpreting price and OI together

“Price up, OI up” is often called long buildup, while “price down, OI up” is often called short buildup. These are market heuristics, not direct observations of trader intent: each contract still creates both sides.

A participant may hedge exposure elsewhere. An options contract may be one leg of a spread. OI does not reveal the whole portfolio or which side initiated the trade.

Indian derivatives checks

Compare the same underlying, expiry, strike and option type at matching timestamps. Near expiry, exposure can move to the next contract; looking at the expiring contract alone can mislead.

Confirm units before comparing vendors. A displayed quantity in underlying units is not necessarily a count of contracts. High OI also does not eliminate slippage: the bid-ask spread and available liquidity at your intended size still matter.

Limitations

  • Check whether a feed reports contracts, lots or underlying units.
  • Expiry, rollover and timestamp differences can distort simple OI comparisons.

Frequently asked questions

Is open interest double-counted for buyer and seller?
A matched outstanding contract is counted once in market OI, although it has both a long and a short counterparty.
Why can volume be high while OI barely changes?
Many trades can transfer existing exposure or offset openings and closings. Volume records activity; OI records the remaining outstanding contracts.
Does high call OI guarantee resistance?
No. Options positions can be hedged, part of spreads or transferred. OI at a strike is not a guaranteed price barrier.
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