Open Interest
The number of derivative contracts currently outstanding. It rises when a new position is opened and falls when one is closed.
Also called: OI · OI buildup · change in OI · open interest analysis
What it means
Open interest counts live contracts, not transactions. A trade between two people who are both opening increases it by one; a trade between two people who are both closing decreases it by one; a trade where one opens and one closes leaves it unchanged. Volume counts all of those identically, which is why the two measure different things.
The standard reading pairs the change in open interest with the change in price. Rising price with rising OI suggests new longs; rising price with falling OI suggests shorts covering. These are interpretations of aggregate data, not observations of who is positioned where.
Open interest is reported with a lag and is revised. Intraday figures are provisional.
How OptionLab Pro’s engine uses it
In the live engine
Per-strike open interest feeds our Max Pain and Put-Call Ratio computation, which runs on the chain rather than on a vendor summary so the inputs are auditable. We never treat an OI concentration as a directional signal on its own — it enters as chain context alongside the three engines, never as a vote.
go/internal/optionchain/maxpain.go (ComputeMaxPainAndPCR)The common mistake
Where traders get this wrong
Treating open interest as a direction indicator. It has no sign: for every long there is a short, and a large number at a strike tells you activity is concentrated there, not which side is right. The price-plus-OI interpretations above are inferences with real exceptions, not rules.
Go deeper
There is a full lesson on this in the Academy, with an interactive widget and a Hindi translation.
Related terms
Educational and analytical content only. OptionLab Pro is not a SEBI-registered investment adviser or research analyst and does not give buy or sell recommendations. Derivatives trading carries a high risk of loss.