Open interest

Also called OI

The number of contracts currently outstanding in a market — positions opened and not yet closed or settled.

Kalshi publishes it per market and this site carries it through on every market row. The distinction from volume is the whole reason to look at it.

Volume counts turnover, so a market maker recycling the same inventory all day can post enormous volume while open interest never moves. Open interest only rises when a new position is created, which requires a buyer and a seller who both want exposure they did not have before. Rising open interest alongside a lopsided taker imbalance is positioning — new money committing to a side. Rising volume with flat open interest is churn, and it usually means the activity you are looking at is liquidity provision rather than opinion.

The limit of the metric is worth stating plainly, because it is often overstated. Every contract has a long and a short, so open interest is symmetric by construction and can never tell you which side the committed capital favors. It tells you how much capital is committed to the question at all. Pair it with taker-side data for direction, and with depth for whether you could join.

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Definitions describe how Polymarket and Kalshi behave and how WhaleTracks models them; venue rules and fee schedules can change, so confirm anything you size a position on with the venue itself. WhaleTracks is informational analytics, not financial advice. Past performance does not guarantee future results.