FIFA World Cup 2026 sent combined Kalshi and Polymarket trading to $44.8 billion in June, up 75% from May. Here is the fee math on what that volume actually cost traders.
According to The Block, Kalshi and Polymarket together recorded $44.8 billion in trading volume during June 2026, a 75% increase from $25.66 billion in May. The World Cup is the primary driver. Kalshi alone reported $31.5 billion in June volume, up 87.4% month over month, and has sustained over $1 billion in daily volume every day since the FIFA World Cup opened on June 11. Polymarket's global platform recorded $10.26 billion, a 45% monthly increase.
For context: total prediction market volume across all platforms in all of 2023 was under $10 billion. June 2026 alone matched that entire year in roughly three weeks.
The scale of individual markets is easier to reason about than the $44.8 billion aggregate.
Polymarket's World Cup Winner market processed $3.9 billion in lifetime trading volume through early July. Kalshi's equivalent winner market recorded $832 million. Combined, those two contracts account for roughly $4.7 billion in trading on a single question.
The World Cup format runs group stage, round of 16, quarterfinals, semifinals, and a final from June 11 through July 19. Markets on individual match outcomes layered on top of the winner contract. Kalshi has sustained over $1 billion in notional daily volume since June 11, an average that held through the group stage and knockout rounds.
Different platforms apply different fee coefficients to sports markets. The formula for both Kalshi and Polymarket is:
taker fee per contract = coefficient × price × (1 − price)
The coefficient determines how much you pay at any given probability. Here is how the three main platforms structure sports taker fees:
| Platform | Fee coefficient | Max fee at 50¢ (per 100 contracts) |
|---|---|---|
| Polymarket global (sports) | 0.03 | $0.75 |
| Polymarket US | 0.05 | $1.25 |
| Kalshi | 0.07 | $1.75 |
The 50-cent scenario is the most expensive point. Most World Cup winner contracts trade far below 50 cents because the field contains 16 or more teams at various stages. A team priced at $0.15 (a realistic price for a favorite in the quarterfinals) produces a lower fee.
Here is a concrete example: a taker order of 200 contracts on "Will France win the 2026 World Cup?" at a price of $0.15 per contract.
| Platform | Calculation | Taker fee |
|---|---|---|
| Polymarket global (sports) | 0.03 × 0.15 × 0.85 × 200 | $0.77 |
| Polymarket US | 0.05 × 0.15 × 0.85 × 200 | $1.28 |
| Kalshi | 0.07 × 0.15 × 0.85 × 200 | $1.79 |
On this trade, Polymarket global charges 57% less than Kalshi. Your $0.15 entry buys 200 contracts; if France wins, you collect $200. The fee is a fixed cost deducted when you execute. Run your exact position size and contract price through the fee calculator to see the net cost before you place.
The same ratio holds at other price points. At $0.50, Polymarket global charges $0.75 per 100 contracts and Kalshi charges $1.75, a 2.3x difference. At $0.30, Polymarket charges $0.63 per 100 and Kalshi charges $1.47. The coefficient gap is constant; the dollar gap narrows as the contract price moves toward 0 or 1.
For the complete Kalshi fee structure including maker fees and volume tier adjustments, see the Kalshi 2026 fee guide. For Polymarket's full category-by-category breakdown covering crypto (1.80% coefficient), politics, economics, and geopolitics (free), see the Polymarket fees guide.
Record trading volume narrows bid-ask spreads. A market with $31.5 billion in monthly Kalshi volume runs deeper order books than a market running at May's $17 billion pace. Spreads on the most active World Cup contracts — winner market, quarterfinal slots, individual match outcomes — tightened through June as order book depth grew.
The practical effect: taker orders fill closer to the theoretical mid-price. Slippage on a 500-contract position in a market with $1 billion in open interest is different from slippage in a market with $5 million. A 0.5-cent tighter spread on a 200-contract position at $0.15 saves $1.00 in execution cost, roughly matching the fee gap between Polymarket global and Kalshi on that trade size.
Tighter spreads do not change the taker fee coefficient, but they reduce all-in execution cost. To model slippage on larger orders, use the PM EV calculator with current order book depth, or check the liquidity deep-dive for how to estimate slippage from order book data before you execute.
The 2.3x fee gap between Polymarket global sports and Kalshi for World Cup contracts creates structural conditions for cross-platform arbitrage when the same contract trades at different prices on each exchange. If Kalshi shows France at $0.34 and Polymarket shows France at $0.33, the 1-cent price difference alone does not cover the fee gap on a round-trip position. At 200 contracts, the price edge yields $2.00 but the fee cost at Kalshi is $1.69 (at $0.34 price) and at Polymarket $0.72, totaling $2.41 in fees — a net-negative trade.
The arbitrage calculator handles cross-platform fee netting automatically. Enter both legs and it tells you whether the price difference survives both taker fees. For World Cup contracts specifically, the Polymarket lower fee coefficient means Polymarket legs of a cross-platform arb cost 57% less in fee drag than the Kalshi leg, which affects which side of an arb you should initiate on which platform.
The World Cup final is July 19, 2026. Markets on the final result, the winner bracket, and individual match outcomes will remain active through that date. After the tournament closes, the high-velocity contract structure driving most of June's volume disappears.
Whether platforms sustain $44.8 billion monthly levels after July 19 depends on what fills the order book next. The $44.8 billion June figure establishes what these platforms can process at full capacity. That is useful information for assessing liquidity risk on any position you hold into the post-tournament period, when order books are likely to thin.