Kalshi and Polymarket's combined volume reaches all-time high in July, surpassing $50 billion

Kalshi and Polymarket saw their combined trading volume soar to a new all-time high in July as prediction markets continued to gain steam around the World Cup.

According to The Block's data dashboard, Kalshi, Polymarket, and Polymarket US posted $50.59 billion in combined monthly trading volume in July, marking a 7.8% increase from June's $46.95 billion monthly volume.

Kalshi remained in the lead, and recorded $37.7 billion in the past month. This marks a 14% month-over-month growth.

Notably, the monthly data indicates a shift in volume between Polymarket and Polymarket US. While Polymarket's monthly volume contracted 26% to $7.9 billion, the U.S. platform saw its volume rise 54% to $5 billion. The combined volume of Polymarket and Polymarket US decreased from $14 billion to $12.9 billion.

The U.S. platform, regulated by the Commodity Futures Trading Commission, dropped its initial waitlist restrictions in May, opening the platform to all U.S. users. This allowed U.S. traders who had previously bypassed regional blocks to participate legitimately on the platform. 

Earlier this year, Rutgers University statistician Harry Crane estimated that U.S. traders drove about 30% of Polymarket's main, offshore platform volume during the 12 months ending April 30, 2026.

World Cup boost

July's overall surge in volume can be attributed to the FIFA World Cup, which started on June 11 and ended on July 19. Kalshi's prediction market on the final match between Spain and Argentina alone drew roughly $1.9 billion. Polymarket's bet predicting the World Cup winner attracted around $4 billion.

Since the end of the World Cup, however, open interest on the three prediction market platforms has dropped significantly, from around $2 billion at the start of July to $1.2 billion by the end of the month.

Despite growing activity and legitimacy, prediction markets continue to face U.S. legal scrutiny, primarily over sports-related contracts. 

Over a dozen state regulators have accused Kalshi and Polymarket of operating unlicensed gambling platforms, taking action to block event contracts in their respective states. In response, the platforms — alongside the CFTC — are contesting these state enforcement actions, arguing that federal oversight preempts state jurisdiction.