Prediction Markets vs. Sportsbooks: The 2026 Growth Comparison
How Kalshi and Polymarket’s growth compares to licensed sportsbooks — volume, legal status state by state, fee structure, and the age gap regulators are racing to close · August 2026
Eighteen months ago, sports prediction markets were a rounding error next to licensed sportsbooks. In 2026 they’re a genuine second market — one growing faster than the regulated industry, fighting off lawsuits in 17 states, and legally open to bettors as young as 18 in a country where every licensed sportsbook requires you to be 21. We pulled together the volume data, the state-by-state legal fight, and the fee structure comparison to show what’s actually happening, not what either side’s marketing says is happening.
Combined Kalshi and Polymarket volume grew from under $5 billion a month to roughly $24 billion a month in seven months, and prediction markets captured 27% of all US sports-betting volume during the 2026 World Cup — up from 9% in January. That works out to $1.71 in prediction-market volume for every $1 wagered through licensed US sportsbooks. Unlike any licensed sportsbook, they’re open to bettors at 18, not 21, and $5.4 billion of Kalshi’s 2026 volume has come from users aged 18 to 21.
The headline numbers
growth in combined Kalshi + Polymarket monthly volume, Sept. 2025 (<$5B) to April 2026 (~$24B)
of all legal US sports-betting volume during the World Cup — up from 9% at the start of 2026
NewBonuses.com Prediction-to-Sportsbook Volume Ratio — prediction-market volume per $1 of licensed sportsbook handle
states currently suing, fining, or trying to block Kalshi and/or Polymarket
minimum age to trade on Kalshi/Polymarket vs. minimum age at any licensed US sportsbook
traded by 18-to-21-year-olds on Kalshi in 2026, $3.9B of it on sports and parlays
The growth curve, and why the World Cup exposed it
Combined Kalshi and Polymarket global trading volume was under $5 billion a month as recently as September 2025. By April 2026 it had climbed to roughly $24 billion a month — nearly a fivefold increase in about seven months (Pew Research Center, May 2026). For context, the total amount wagered through licensed US sportsbooks averaged around $14 billion a month in 2025. Prediction markets, which barely registered as a category two years ago, are now moving more money globally per month than the entire regulated US sports betting industry handles domestically.
The 2026 World Cup made the shift visible in a single data point regulators couldn’t ignore: prediction-market activity went from roughly 9% of all legal US sports-betting volume at the start of the year to about 27% during the tournament (Fortune, July 2026). Kalshi repeatedly broke its own trading records during the World Cup, at one point operating at nearly ten times its volume from earlier in the year, and had more daily active users on its mobile app than either DraftKings or FanDuel — the two largest licensed US sportsbooks — for stretches of the tournament. Kalshi also outpaced Polymarket directly during the Cup, generating more than twice Polymarket’s trading volume over the same window.
Sports is now the dominant category on Kalshi specifically: roughly 80% of its volume between mid-2024 and April 2026 came from sports contracts, versus 39% for Polymarket, where politics (32%) and crypto (20%) still make up a larger share. That split matters for how directly each platform actually competes with a sportsbook — Kalshi, more than Polymarket, has effectively become one.
The Prediction-to-Sportsbook Volume Ratio
Putting Pew Research’s combined-volume figure next to the American Gaming Association’s licensed-handle figure produces a comparison nobody else has run: at $24 billion a month in prediction-market volume against roughly $14 billion a month in licensed US sportsbook handle, Kalshi and Polymarket combined are now moving about $1.71 for every $1 wagered through the entire licensed US sports betting industry. That’s the NewBonuses.com Prediction-to-Sportsbook Volume Ratio, and the context that makes it striking: prediction markets reached that scale while being legally restricted, fined, or actively shut down in 17 states, while every licensed sportsbook operates with a full state license everywhere it’s live. A market operating under legal siege in a third of the country is nonetheless outpacing, in raw dollar volume, an industry with no such restriction anywhere it operates.
Prediction-to-Sportsbook Volume Ratio — combined Kalshi + Polymarket global monthly volume (~$24B, April 2026) divided by average licensed US sportsbook monthly handle (~$14B, 2025). Methodology below.
The legal war: 17 states, one federal regulator, no resolution yet
Prediction markets operate under CFTC oversight as federally regulated financial exchanges, not as state-licensed sportsbooks — and that distinction is now the subject of active litigation in roughly a third of the country. As of August 2026, 17 states have sued, fined, issued cease-and-desist orders, or opened formal investigations against Kalshi and/or Polymarket, arguing their sports contracts are unlicensed gambling subject to state law: Arizona, California, Connecticut, Illinois, Maryland, Massachusetts, Michigan, Minnesota, Nevada, New York, Ohio, Rhode Island, Tennessee, Texas, Utah, Washington, and Wisconsin. In several of those states — Connecticut, Illinois, Tennessee, and others — the CFTC has countersued and won injunctions blocking state enforcement, arguing federal jurisdiction preempts state gambling law entirely. In others, the state has won: Massachusetts and Nevada both secured injunctions against Kalshi, and a Michigan court ordered a temporary shutdown. Ohio fined Kalshi $5 million for allegedly evading the state’s 20% sports betting tax and failing age-verification requirements. Minnesota became the first state to pass an outright ban, but a federal judge blocked enforcement on the same federal-jurisdiction grounds.
The remaining 34 states currently allow both platforms to operate without reported restriction — meaning, for now, where you live still determines which set of rules applies to the exact same product. A full state-by-state table is below.
The age gap regulators are racing to close
This is the sharpest structural difference between the two markets, and it’s the one getting the least attention relative to its size. Every licensed US sportsbook requires bettors to be 21. Kalshi and Polymarket, regulated as financial exchanges rather than gambling operators, only require users to be 18 — the same minimum age as opening a brokerage account. That gap is not theoretical: users aged 18 to 21 have traded $5.4 billion on Kalshi in 2026 alone, $3.9 billion of it on sports and parlay-style contracts, representing about 3.14% of the platform’s total volume. American Gaming Association president Bill Miller put the concern bluntly: “Their freshman can use Kalshi to bet on football” despite being legally barred from any licensed sportsbook. Novig CEO Jacob Fortinsky, who runs a competing exchange, described college-age adults as “particularly susceptible to irresponsible trading behavior,” and gaming consultant Jonathan Michaels expects the numbers to grow further once football season is in full swing.
Whether this counts as a loophole or simply a different, federally settled regulatory framework is exactly what the 17-state legal fight above is arguing about. Either way, it’s a real, quantified, and current gap between how the two markets are allowed to treat the same 18-to-20-year-old bettor.
Fee structure: neither side is simply “cheaper”
A common claim in prediction-market marketing is that trading fees beat sportsbook vig outright. The real comparison is closer than that. A standard sportsbook line (-110 on both sides of a spread) implies roughly 52.4% probability per side, a combined 104.8% — meaning the book takes roughly 4.5 cents of every dollar wagered, though hold runs meaningfully higher on player props and parlays. Kalshi’s standard exchange fee is calculated as roughly 7% of price times (1 minus price) per contract, which on a liquid 50-cent contract works out to about 1.75 cents — cheaper than sportsbook vig on that specific trade. But on thinner markets, the bid-ask spread itself can add several more cents round-trip, at which point the effective cost can exceed what a sportsbook would have charged on the same bet. In practice: patient traders on liquid Kalshi markets often pay less than sportsbook vig; casual bettors on thin or exotic markets often don’t.
How this comparison was built
Volume data. Combined and platform-level trading volume figures are drawn from Pew Research Center’s May 2026 analysis (based on Kalshi’s and Polymarket’s own published trade data) and from Kalshi’s 2026 year-to-date volume as reported by CNN Business/KVIA (August 2026). World Cup-specific volume and market-share figures are drawn from Sportico and Fortune’s July 2026 coverage. Licensed-sportsbook handle figures are drawn from the American Gaming Association’s 2025 full-year commercial gaming report as compiled by Track360.
Legal status. State-by-state litigation status compiled from CBS Sports’ August 2026 tracker, cross-referenced against direct state attorney general and CFTC filings where cited in that reporting. Legal status changes quickly in this category — several cases are on active appeal — so status should be re-verified before citing beyond publication date.
Age-gap data. Figures on under-21 trading volume, its share of Kalshi’s total volume, and the sports/parlay breakdown are drawn from CNN Business’ August 28, 2026 reporting, which cited Kalshi’s own disclosed figures. Quotes are as reported in that same coverage.
Fee comparison. Sportbook hold/vig figures use standard -110 two-sided market math. Kalshi fee figures use the platform’s published standard fee schedule as summarized by OddsShopper’s 2026 analysis; actual costs vary by specific market liquidity and contract price.
Volume Ratio calculation. The $1.71-to-$1 figure divides Pew Research Center’s reported combined Kalshi + Polymarket global monthly trading volume (~$24B, April 2026) by the American Gaming Association’s 2025 average monthly licensed US sportsbook handle (~$14B). The two figures come from different reporting periods (April 2026 vs. full-year-2025 average) and different geographic scopes (prediction-market volume is global, sportsbook handle is US-only), so this ratio is a directional comparison of scale, not a precise same-period, same-market measurement — a limitation we’re stating plainly rather than smoothing over.
Limitations. This is a snapshot as of August 2026. Both the volume figures and the legal landscape are moving quickly — several of the lawsuits referenced are on active appeal and could resolve in either direction. Figures reported by the platforms themselves (Kalshi’s own volume and age-breakdown disclosures) have not been independently audited.
State-by-state legal status
Citation & reuse. This comparison was produced by NewBonuses.com (August 2026), drawing on primary and secondary sources including Pew Research Center, Sportico, Fortune, CBS Sports, CNN Business, the American Gaming Association’s 2025 commercial gaming report, and OddsShopper’s fee analysis. The findings, tables and figures are free to cite, quote and reference with attribution and a link to this page. Journalists and researchers may contact us through the site for the underlying sourcing.