Prediction Markets vs Sportsbooks: What the Vig Gap Actually Means

A prediction market and a sportsbook both let you bet on a sports outcome. The structural differences between them are large enough to change where you put your money. For serious bettors, those differences are worth understanding at the mechanics level.

Below is a breakdown of how each model prices risk, who the counterparty is, what happens to winning accounts, what the position constraints look like in practice, and where the market-efficiency research points in 2026.

The Two Business Models

A sportsbook is a principal. When you bet -110 on a side, the book is your counterparty. The book takes your money, holds it, and pays you back if you win. The book sets the price, accepts the bet onto its own balance sheet, and manages the position across thousands of customers. Its goal is to shade lines in its direction, extract vig, and run out players whose edge is real.

A prediction market is an exchange. On Kalshi, you buy a binary contract from another user who holds the opposing side. The exchange never takes a position. Its revenue comes from fees, not from the outcome of any event. When you win, another user loses. The exchange has no financial incentive to remove you from the platform.

This is the core structural difference, and every other comparison flows from it.

The Vig Calculation

The standard -110/-110 market at a US sportsbook encodes a specific fee. Here is the exact calculation:

• Implied probability for each side: 110 / (110 + 100) = 52.38%
• Sum of both sides: 52.38% + 52.38% = 104.76%
• Overround: 4.76%, the house's extraction before any outcome resolves

That 4.76% is extracted on every dollar wagered, regardless of your accuracy on any individual game. A bettor who breaks even on raw win-loss outcomes still loses 4.76% of volume over time.

A measured sample of 64 NBA, NHL, and MLB markets on Kalshi during March and April 2026 showed Kalshi's average vig at 0.85%, against 4.62% on concurrent sportsbook lines for the same events. The gap is 3.77 percentage points on every dollar in action.

The mechanism behind the tighter spread is the limit order book. When you post a limit order as a maker on Kalshi, you set the price. The spread between your bid and the best ask is typically $0.01 on liquid contracts. At a $0.50 price, that is a 2% round-trip spread, but only the side taking the market pays the spread. The maker pays nothing on execution. Posting your own price, waiting for a fill, brings your effective vig near zero on that leg.

Account Access: Who Gets Limited

The most reliable problem for serious US sports bettors is account restriction. Sportsbooks limit winning accounts aggressively. AI profiling models have compressed the timeline: accounts get flagged after a handful of sharp plays, sometimes within weeks of opening.

Being limited does not require professional-level edge. A recreational bettor who consistently beats the closing line gets reduced to $20 limits without formal notice. The sportsbook's interest is straightforward: remove players whose expected value is negative for the house.

Kalshi is structurally incapable of this. Every winning contract pays out of the counterparty's position, not the exchange's capital. There is no incentive to remove winning traders. The only constraints are position size and order book depth. You are not removed from the platform for winning.

For any bettor who has been limited at multiple books, this access has a direct dollar value. An edge at a sportsbook where your limit is $20 is functionally worthless. The same bet placed at full size on Kalshi, where the market maximum is $25,000 per event, recovers the edge without requiring a new account.

What You Give Up: Position Limits and Liquidity

Kalshi is a CFTC-regulated Designated Contract Market. Federal regulations require position limits on event contracts to prevent excessive speculation and market manipulation. The cap on most Kalshi sports markets is $25,000 per event payout.

The position limit math:

• Buying Yes at $0.65 to reach the $25,000 payout cap: you need 25,000 contracts at $0.65 = $16,250 at risk
• Buying Yes at $0.50 to reach $25,000 payout: you need 25,000 contracts at $0.50 = $12,500 at risk
• For a bettor staking $500/game: the $25,000 cap equals 50 standard units. No practical constraint.
• For a bettor staking $5,000/game: the $25,000 cap equals 5 standard units. A real ceiling.

High-stakes bettors hit this ceiling on any single market. A traditional sportsbook does not carry a federally mandated payout cap, though it manages its own limits internally, applied selectively against winning accounts. The prediction market's limit is universal and structural. The sportsbook's limit is selective and punitive.

Liquidity is the second gap. Kalshi depth on primetime NFL, NBA, and MLB games is sufficient for most mid-volume bettors. Kalshi depth on lower-tier college games, player props, and niche leagues is thin. The order book on a Tuesday conference basketball game shows a few hundred dollars at the best bid and ask. Any size beyond that moves the market against you.

Sharp-facing sportsbooks like FanDuel quote two-sided markets across a far wider range of events and bet types. For illiquid markets and prop bets, a sharp sportsbook with real depth remains necessary.

The Favorite-Longshot Bias: Where Kalshi Markets Are Mispriced

Prediction markets are not perfectly efficient. Research published in 2026 documents a specific, persistent pricing error on Kalshi that bettors need to understand before placing money.

Burgi, Deng, and Whelan's paper "Makers and Takers: The Economics of the Kalshi Prediction Market" (January 2026) analyzed over 300,000 contracts on the platform. The core finding: a clear favorite-longshot bias. Low-price contracts win far less often than their price implies. Buyers of contracts priced below $0.10 lose more than 60% of their money over time. Those contracts resolve in their favor far less than 10% of the time.

The paper separates participants by behavior:

Takers lose more than three times as much as makers. The bias is concentrated among takers buying longshot contracts. Makers who post offers on favorites, contracts priced above $0.65, show losses close to the exchange fee and near-zero predictive error within one hour of resolution.

The practical translation: on Kalshi, post limit orders rather than taking the best ask. If you are betting favorites, the bias works in your direction. If you routinely buy contracts below $0.15, the structural mispricing is working against you before vig is even counted.

This pattern is not unique to Kalshi. Justin Wolfers and Eric Zitzewitz documented the favorite-longshot bias across multiple market types in their 2004 survey "Prediction Markets" (Journal of Economic Perspectives, 18(2):107-126). The 2026 Kalshi data confirms the bias remains live and quantifiable on the largest US regulated prediction market. Now there is enough data to trade around it.

Geographic Access

As of June 2026, Kalshi operates in over 40 US states, including California and Texas, where DraftKings and FanDuel do not have legal sportsbook licenses. The Third Circuit Court of Appeals affirmed CFTC exclusive jurisdiction over Kalshi's sports event contracts in April 2026, preempting state gambling laws.

For bettors in states with restrictive gambling legislation, prediction markets are not a secondary option. They are the primary regulated venue for sports event contracts. The Congressional Research Service noted in March 2026 that 87% of Kalshi's $39.7 billion in trailing-year volume was in sports markets. That scale reflects genuine demand. The combination of geographic access, low vig, and no-ban structure makes prediction markets a first-line resource for bettors in states where traditional books remain unavailable.

Regulatory Outlook

The CFTC scrapped its June 2024 proposed restrictions on sports event contracts in January 2026 and announced a new rulemaking framework. CFTC proposals in 2026 include prohibiting injury-specific props and certain derivative market types, but the core sports contract category is not on the table for elimination.

Bettors who defer engagement with prediction markets until full regulatory clarity pay a measurable vig premium in the interim. The structural advantages of the exchange model do not depend on regulatory permanence. They derive from the peer-to-peer contract design and the CFTC's explicit classification of these instruments as regulated futures contracts.

Which Bets Go Where

The right approach is not a binary choice between prediction markets and sportsbooks. Each venue has structural advantages for specific bet types.

Use Kalshi for:

• Major-league game sides (NFL, NBA, MLB, NHL primetime) where order book depth is sufficient
• Positions under $25,000 per event, where the federal payout cap does not constrain most bettors
• Markets in states without legal sportsbooks
• Any bet where you have been limited at major books and need access to full size

When placing on Kalshi, post limit orders, not market orders. The maker-taker difference is 22 percentage points in average loss. Letting other users come to your price is not optional if you want to capture the vig advantage.

Use a sharp sportsbook for:

• Player props, same-game parlays, and futures, which Kalshi does not offer in equivalent depth
• Lower-tier college games and niche markets where Kalshi liquidity is thin
• Positions above $25,000 per event where you need size beyond Kalshi's cap

Over a 52-week year at $10,000 monthly betting volume, shifting $6,000 of that monthly action from a standard sportsbook to Kalshi on liquid major-league sides saves roughly $2,300 in annual vig at the measured 3.91 percentage-point differential. No increase in predictive accuracy required. Routing the right bet type to the right platform is the entire mechanism.

The maker-taker split adds a second layer: on Kalshi, your execution method shapes your effective cost as much as the vig rate does. Post limit orders on favorites, let the takers come to you, and the structural advantage of the exchange compounds over volume.