Glossary › Open interest
Checked September 25, 2026 · 3 sources · plain-English definition, not financial advice
Open interest: The number of Kalshi contracts in a market that are still held open, not yet closed out or settled; it rises when new positions are opened.
The CFTC glossary defines open interest as the total number of contracts entered into and not yet liquidated by an offsetting trade or fulfilled by delivery. Kalshi's API reports it for every market, described as the number of contracts bought on the market without taking netting into account.
Open interest and volume answer different questions. Volume counts every contract traded, while open interest counts what is still outstanding. Example: you buy 100 Yes and the other side opens 100 No, so open interest rises by 100. If you later sell your 100 Yes to a new buyer, volume rises by another 100 but open interest does not change, because the position just changed hands.
Kalshi's rulebook requires that members can see open interest and trade volume along with the best bid and offer. What to check: a market with high open interest but a thin order book can still be hard to exit, so look at depth too.
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Checked September 25, 2026. Kalshi changes fees, rules, funding options and limits; the market's rules, the order ticket and Kalshi's help center are the final word.
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