Kalshi retains commanding US volume lead as Polymarket US grows faster
Kalshi logged about 65 billion dollars in October volume, about 10 percent above September, while Polymarket US recorded 10 billion dollars, up about 15 percent. Among U.S.-regulated platforms Kalshi held about 83 percent share, with 2.05 billion dollars in open interest versus 384 million dollars at Polymarket US.
Kalshi recorded about 65 billion dollars in October trading volume, an increase of about 10 percent from September, according to CryptoBriefing. Polymarket US posted 10 billion dollars, rising about 15 percent over the same period.
Polymarket US therefore grew faster in percentage terms, but its monthly trading activity remained substantially below Kalshi’s. The figures distinguish growth momentum from the scale of each platform’s business.
Volume and open interest favor Kalshi
Among U.S.-regulated platforms, Kalshi held about 83 percent market share, according to CryptoBriefing. That figure applies specifically to the regulated U.S. segment, rather than prediction markets as a whole.
Kalshi also had 2.05 billion dollars in open interest, compared with 384 million dollars at Polymarket US. Alongside the October volume totals, those balances show Kalshi leading on both reported measures despite Polymarket US’s stronger percentage growth.
What it means for prediction markets
- Growth and market leadership remain distinct: Polymarket US’s roughly 15 percent monthly volume increase exceeded Kalshi’s roughly 10 percent gain, without closing the substantial gap in reported activity.
- Scope matters for market-share comparisons: Kalshi’s approximately 83 percent share describes U.S.-regulated platforms and should not be treated as a global figure.
- Open interest adds a separate comparison: The 2.05 billion dollars at Kalshi versus 384 million dollars at Polymarket US provides another measure of their relative scale beyond monthly trading volume.
Sources & attribution
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