Kalshi posts a $19.03B week, Polymarket US hits $2.72B in the same week

Kalshi recorded $19.03 billion in weekly notional trading volume from October 5 to 11, 2026, according to Crypto Briefing. The accompanying headline snapshot puts Polymarket US at $2.72 billion for the same week, although the supplied Crypto Briefing report does not substantiate that figure or explain its measurement basis.

Records driven by combo contracts

In an October 13 report, Crypto Briefing’s Estefano Gomez said the CFTC-regulated platform registered $3.91 billion on October 10, 2026, and $3.96 billion on October 11. Both exceeded the previous daily record of $3.68 billion, established on October 4.

Parlay-style combo contracts represented approximately 70% of volume on both record days, with reported contributions of about $2.80 billion and $2.75 billion, respectively. Many were long-shot combinations priced below 1 cent. Kalshi introduced its combo products in 2025 and has expanded its sports offerings, according to Crypto Briefing.

That product mix is important when interpreting the totals. Notional volume measures a contract’s full potential payout rather than the amount a trader pays to enter the position. Low-priced combinations can therefore generate substantial reported volume while putting considerably less trader capital at risk.

Football activity and regulatory exposure

Kalshi’s trailing 30-day volume exceeded $73 billion, while its year-to-date cumulative activity reached the hundreds of billions, Crypto Briefing reported. Daily volume has surpassed $3 billion several times since mid-September. With the NFL and NCAA football seasons under way, combined weekend activity across Kalshi and Polymarket exceeded $8.5 billion, with football contributing substantially.

The growth also puts greater attention on Kalshi’s regulatory position. It operates under federal CFTC oversight, while US sports wagering is regulated at the state level. Its sports contracts face continuing legal scrutiny from critics who consider them sports bets; the increasing prominence of multi-leg combinations makes that distinction particularly consequential.

What it means for prediction markets

• Notional volume is not cash committed. The roughly 70% combo share on the two record days limits what the headline totals reveal about trader capital at risk.
• Platform comparisons need consistent definitions. The $2.72 billion Polymarket US figure lacks supporting methodology in the supplied report, limiting direct comparison with Kalshi’s weekly notional total.
• Sports products link growth to legal outcomes. Restrictions on Kalshi’s sports or combo offerings could affect the products responsible for much of its record daily volume.