A $100 bet on a -110 NFL spread at DraftKings costs you $10.34 in implied vig before the game even kicks off. The same $100 position on Kalshi or Polymarket typically costs $1-3 in fees. That gap is the entire reason prediction markets have pulled in $63.5 billion in volume in 2025, up from $15.8 billion the year before, and why sportsbooks are watching their margins nervously.
This isn't a philosophical debate about which product is more fun. It's a math problem. Sportsbooks and prediction markets both let you bet money on outcomes, but they price risk in fundamentally different ways, and that difference determines how much of your money you keep over a thousand bets. If you've been betting NFL spreads for years and you're wondering whether Kalshi or Polymarket is worth switching to, the numbers below answer that directly.
The short version: prediction markets almost always cost less per trade, tax treatment is murkier on both sides, and sportsbooks still win on same-game parlays and live betting speed. For a broader legal and structural breakdown of the two industries, see our deep dive on prediction markets vs sports betting. Below, we go category by category with actual numbers.
Quick Comparison
| Category | Prediction Markets (Kalshi/Polymarket) | Sports Betting (DraftKings/FanDuel) |
|---|---|---|
| Pricing model | Order book, peer-to-peer | Fixed odds set by book |
| Typical cost per $100 | $1-3 (fees) | $9-10 (vig baked into odds) |
| Regulator | CFTC (Kalshi) | State gaming commissions |
| Available states | 40+ (Kalshi), most states (Polymarket) | Varies, 38 states have legal sports betting |
| Tax reporting | 1099-MISC (Kalshi), none (Polymarket) | W-2G above thresholds |
| Same-game parlays | Rare/limited | Core product |
| Live/in-play betting | Limited | Extensive |
| Markets beyond sports | Politics, economics, weather, crypto | Sports and some entertainment props |
Why This Comparison Matters Now
Sports make up more than 80% of all prediction market volume today, which means Kalshi and Polymarket aren't a niche alternative anymore — they're direct competitors to DraftKings and FanDuel for the same customer. Monthly active wallets across prediction markets hit 840,000 as of early 2026, according to TRM Labs, and combined monthly volume between Kalshi and Polymarket alone reached roughly $20 billion in February 2026. Regulators are paying attention too: eleven states introduced legislation in 2026 specifically addressing whether prediction markets should be treated like gambling or like regulated derivatives, and Arizona filed criminal charges against Kalshi on March 18, 2026, over exactly this question.
For bettors, the practical question is simpler than the regulatory fight. If you're placing $50-200 a week on NFL or NBA outcomes, does routing that money through a prediction market instead of a sportsbook actually save you money, and what do you give up to get there. We ran the numbers on fees, odds structure, and after-tax outcomes to answer it plainly.
Fees and the Vig Problem
Sportsbooks make their money through the vig — the built-in margin on every line. A standard -110/-110 spread bet means you risk $110 to win $100 on both sides, which translates to roughly a 4.5% house edge per bet once you account for the true 50/50 probability. Moneyline and prop bets often carry worse hold, sometimes 6-8%, especially on same-game parlays where books stack correlated legs to inflate their edge.
Prediction markets work differently because they're order books, not fixed-odds books. On Kalshi, fees run around $0.02 per contract on a variable schedule tied to price, which on a typical $1 contract works out to a low single-digit percentage. Polymarket charges taker fees between 0.75% and 1.80% depending on category as of the March 30, 2026 fee expansion, with maker orders free and eligible for 20-50% rebates. See our full breakdown in Polymarket fees explained and Kalshi fees explained for exact schedules by market type.
The Catch: Prediction market pricing looks cheaper on paper, but liquidity matters. A thin order book on a niche NFL prop can have a wide bid-ask spread that eats into your effective cost just as much as sportsbook vig — you're just paying it to another trader instead of the house. Stick to liquid markets (major game outcomes, not obscure player props) if you want the fee advantage to actually show up in your results.
Odds Structure: Fixed Lines vs Live Pricing
Sportsbook odds are set once and move in discrete steps — a line might shift from -3 to -3.5 overnight, but you're locked into whatever price you clicked. Prediction market prices move continuously, tick by tick, as traders place orders, which means the contract price you see is closer to a real-time consensus probability than a bookmaker's opinion.
This matters for accuracy. Polymarket's Brier scores across major 2025-2026 events sit around 0.09, translating to roughly 94%+ calibration accuracy on binary outcomes — meaning when the market says 70%, the event happens close to 70% of the time. Sportsbook lines are calibrated to balance action and protect the house, not to be maximally accurate, so they can diverge from true probability especially on lopsided public bets.
Concrete Example: Say the Chiefs are 65% favorites by true probability to beat the Broncos. A sportsbook might price the moneyline at -160 (implying ~61.5%) partly because public money floods the favorite regardless of price, baking in extra margin. A prediction market contract on "Chiefs win" would likely trade closer to $0.65, reflecting actual market consensus rather than a house-adjusted number. Over hundreds of bets, that gap compounds.
Regulation and Legality
Sports betting legality is settled and boring at this point — 38 states have some form of legal sports wagering, regulated by individual state gaming commissions, with clear licensing and consumer protections. Prediction markets are still fighting this battle state by state. Kalshi operates as a CFTC-regulated designated contract market, which the company argues preempts state gambling law entirely, a position CFTC Chairman Selig has publicly supported.
Not every state agrees. Tennessee ruled in Kalshi's favor, but Nevada, Massachusetts, Maryland, and Ohio have ruled against it, and the Schiff-Curtis "Prediction Markets Are Gambling Act" introduced March 23, 2026 would classify these products as gambling outright if passed. For the complete state-by-state breakdown, check our prediction markets legal states map and the broader are prediction markets legal in the US guide. Polymarket's legal footprint is different again — see where Polymarket is legal for the current access map.
Prediction markets win on pricing transparency. Sports betting wins on regulatory certainty.
Tax Treatment: Neither Side Is Clean
Sports betting tax reporting is at least established. Sportsbooks issue a W-2G for wins over $600 at 300-to-1 odds or more, and gambling losses are deductible against winnings if you itemize — though the One Big Beautiful Bill Act's 90% gambling loss cap, starting tax year 2026 and filed in 2027, limits how much of those losses you can actually write off.
Prediction markets are messier. The IRS has issued zero formal guidance on how to treat prediction market contract winnings specifically, leaving three plausible treatments in play: ordinary income (the safest default), gambling income (unfavorable given the new loss cap), or Section 1256 contract treatment (aggressive, potentially favorable, and legally uncertain). Kalshi issues a 1099-MISC, so the IRS already knows what you made. Polymarket issues nothing globally, which doesn't mean the income is untaxed — it means you're on your own to report it correctly. Our full prediction market taxes guide walks through all three treatments and how to file.
The Catch: Don't assume Polymarket's lack of a 1099 means invisibility. The IRS has pursued unreported gambling and crypto income aggressively in recent years, and self-reporting under Schedule 1, Line 8z as "Other Income" is the safest path regardless of which platform you use.
Same-Game Parlays and Live Betting
This is where sportsbooks still dominate outright. DraftKings and FanDuel built entire product lines around same-game parlays, letting you stack a quarterback's passing yards, a receiver's touchdown, and the game total into a single ticket with inflated combined odds that favor the house heavily. Live, in-play betting with sub-second odds updates is another sportsbook strength — you can bet on the next play, the next possession, the next made basket, all with instant settlement.
Prediction markets don't really do this yet. Order books for granular in-game props are thin or nonexistent on Kalshi and Polymarket, and the infrastructure for instant live-market creation lags far behind what DraftKings has built over a decade. If same-game parlays and live betting are your primary use case, a prediction market isn't currently a full substitute — see our comparison of best prediction markets for sports betting for which platforms come closest.
Platform Overlap: Robinhood, DraftKings, and Kalshi Converging
The lines are blurring fast. Robinhood now runs a prediction hub powered by Kalshi's infrastructure, effectively bringing prediction market pricing into a mainstream trading app — our Robinhood vs Kalshi comparison covers whether that's worth using over Kalshi directly. FanDuel launched FanDuel Predicts as its own entry into this space, reviewed in depth in our FanDuel Predicts review, and DraftKings has its own predictions product covered in our DraftKings Predictions review.
This convergence tells you where the industry is heading: sportsbooks want prediction market margins, and prediction markets want sportsbook liquidity and parlay products. Whichever side wins that fight first will likely absorb the other's customer base.
Platform Summaries
Kalshi is CFTC-regulated, available in 40+ states, and pays roughly 4% APY on idle cash sitting in your account — a real advantage over sportsbooks, which pay nothing on unused balances. Its 2025 revenue hit approximately $260 million, and the company raised $1 billion at an $11 billion valuation in December 2025. Full details in our Kalshi review.
Polymarket runs on USDC via Polygon settlement, carries no interest on idle balances, and recently acquired QCEX for $112 million specifically to secure a CFTC license and operate onshore in the US. ICE has invested up to $2 billion in the platform, and it's seeking a roughly $20 billion valuation. Read the full Polymarket review for the complete picture, and see is Polymarket legit if you're still deciding whether to trust it with real money.
DraftKings and FanDuel remain the default for anyone who wants same-game parlays, live betting, and instant cashouts, with decades of consumer protection infrastructure and clear state licensing behind them. What they don't offer is the pricing transparency or fee advantage that prediction markets bring to straightforward win/loss bets.
Verdict: Which One Should You Use
If you bet straightforward game outcomes — moneylines, spreads, totals — and want the lowest cost per bet, use a prediction market. The fee math favors Kalshi or Polymarket on almost every liquid game.
If you rely on same-game parlays, live in-play betting, or same-day cashouts, stick with DraftKings or FanDuel. Prediction markets simply haven't built that product yet.
If you're serious about maximizing edge across sports, run both. Use a sportsbook for parlays and live action, and route your straight bets through Kalshi or Polymarket where the fee structure works in your favor. For a side-by-side of the two biggest prediction market players specifically, see Polymarket vs Kalshi.
Frequently Asked Questions
Is betting on prediction markets cheaper than sports betting?
Yes, on most liquid straight bets. Sportsbook vig typically runs 4.5-8% depending on the bet type, while Kalshi and Polymarket fees run 1-3% on comparable positions. Thin markets can erase this advantage through wide bid-ask spreads, so stick to major game outcomes for the best pricing.
Are prediction markets legal for sports betting?
It depends on the state. Kalshi operates as a CFTC-regulated exchange and argues federal preemption over state gambling law, a position several states dispute — see our prediction markets legal states map for current status by state.
Do I have to pay taxes on prediction market winnings the same way as sports betting?
No, treatment differs and remains unsettled. Sports betting has established W-2G reporting, while the IRS has issued zero formal guidance on prediction market contracts, leaving ordinary income, gambling, or Section 1256 treatment all technically in play. Our prediction market taxes guide breaks down which approach is safest.
Can I do same-game parlays on Kalshi or Polymarket?
Not really. Both platforms focus on single-outcome contracts rather than stacked, correlated same-game parlays, which remain a sportsbook specialty at DraftKings and FanDuel.
Which platform has better odds accuracy, sportsbooks or prediction markets?
Prediction markets generally price closer to true probability because odds move continuously based on trader consensus rather than house-set margins. Polymarket's Brier scores of roughly 0.09 across 2025-2026 events translate to over 94% calibration accuracy on binary outcomes.
Does Kalshi pay interest on my account balance like a savings account?
Yes, Kalshi pays approximately 4% APY on idle cash sitting in your account, which is a real advantage over sportsbooks that pay nothing on unused deposits. Polymarket, by contrast, pays 0% interest on idle USDC balances.
Should I use Robinhood or Kalshi directly for prediction market sports betting?
Robinhood's prediction hub runs on Kalshi's underlying infrastructure, so pricing and markets are largely the same, but the interface and account experience differ. See our full Robinhood vs Kalshi comparison to decide which fits your workflow better.
What's the biggest downside of switching from sports betting to prediction markets?
You lose access to same-game parlays and fast live betting, both of which remain sportsbook strengths. You also take on more legal ambiguity depending on your state, since prediction market regulation is still being litigated in several jurisdictions.
