Polymarket Holds $2B World Cup Book; Kalshi Tops Fees

Polymarket’s single World Cup-winner market has accumulated about $2 billion in lifetime volume, with roughly $436 million in available liquidity and a reported single-day trade of about $137 million. Kalshi runs 48 World Cup markets and has accumulated roughly $182.3 million across those events. Polymarket lists more than 330 active World Cup markets in total.

Industry figures for May put prediction-market notional turnover at $31.2 billion and industry open interest near $1.3 billion. Kalshi accounted for approximately 58% of May volume, about $18 billion, while Polymarket accounted for roughly 28%, about $8.8 billion.

On Kalshi, sports trading reached $10.44 billion in May. Kalshi’s elections category recorded $173.66 million, crypto markets did about $2.02 billion, and a sports-adjacent “exotics” category added $4.88 billion that month.

Polymarket’s World Cup-winner market is roughly 11 times larger than Kalshi’s biggest single World Cup event on the platform. Both platforms price the tournament similarly: Spain is listed near a 17% implied win probability, and Kalshi’s payout on Spain and France is shown at about 5.56x.

May fee totals diverged sharply. Kalshi collected $137.86 million in trading fees in May. Polymarket’s trading fees for the same month totaled $28.07 million. A smaller platform, Opinion, reported $159,330 in fees for May.

Polymarket’s category volumes earlier in 2026 show sports leading the platform. In January, sports accounted for $6.2 billion of a $14.34 billion monthly total. Sports peaked in March at $8.77 billion of a $19.58 billion month. By early June overall activity on Polymarket had declined to about $5.91 billion, with sports representing about 56.5% of that volume; crypto stood at $1.73 billion and politics at $831.25 million.

On Opinion, a week in January included $729.52 million in crypto volume. By the week of June 1, sports made up 99.4% of activity on Opinion and crypto volume fell below $500,000 for that week.

Industry metrics in May show sports accounted for the largest share of volume across the main platforms. Trading data through the group stage and knockout rounds will record how volumes and fees change as the tournament proceeds.