Prediction Market Arbitrage: How to Find Risk-Free Opportunities

Prediction markets have exploded in popularity. Polymarket alone processed billions in volume during the 2024 US election, and platforms like Kalshi, PredictIt, and Metaculus have brought prediction trading mainstream. With that growth comes a familiar opportunity: when different platforms price the same outcome differently, you can lock in guaranteed profit.

This is prediction market arbitrage, and it works on the same mathematical principles as traditional sports betting arbitrage, just across a different set of platforms.

How prediction market arbitrage works

A prediction market lets you buy "yes" or "no" shares on whether an event will happen. Shares pay out $1 if correct, $0 if wrong. If you buy a "yes" share at $0.60, you're betting 60 cents to win $1 (implied probability: 60%).

Arbitrage exists when the combined cost of covering all outcomes across different platforms is less than $1.

Simple example:

Buy "Yes" on Kalshi at $0.48. Buy "No" on Polymarket at $0.48. Total cost: $0.96. One of these pays $1 no matter what. Guaranteed $0.04 profit per share (4.2% return).

Types of prediction market arbitrage

Cross-platform prediction market arbs

The most straightforward type. The same question appears on multiple platforms at different prices. Common with political events, economic indicators, and cultural markets that overlap across Polymarket, Kalshi, and other platforms.

Where to look:

• US elections and political events (covered by all major platforms)
• Economic data releases (Fed rate decisions, inflation numbers)
• Sports championship winners and awards (overlap with traditional sportsbooks)
• Cultural events (Oscar winners, tech product launches)

The trick is finding identical or functionally identical markets. "Will the Fed cut rates in June 2026?" on Polymarket and "Will the Federal Reserve lower the target range at the June 2026 FOMC meeting?" on Kalshi are the same bet, but price differences can exist.

Prediction market vs. sportsbook arbs

More relevant for sports bettors: when a prediction market offers a price on the same outcome as a sportsbook, you can arb between them.

Example:

A sportsbook offers the Lakers to win the NBA Championship at +800 (implied probability 11.1%). Polymarket has "Lakers win NBA Championship" trading at $0.08 (8% implied).

These aren't directly arbitrageable (both sides think the Lakers are unlikely), but if you find the opposite:

• Sportsbook: Lakers to win at +400 (20% implied)
• Prediction market: "Lakers win" No shares at $0.75 (25% implied for "No")

Buy the Lakers at +400 on the sportsbook ($100 to win $400). Buy "No" on the prediction market for $0.75/share, 133 shares ($100).

• If Lakers win: sportsbook pays $500, prediction market loses $100. Net: +$300.
• If Lakers lose: sportsbook loses $100, prediction market pays $133. Net: +$33 on prediction market, -$100 on sportsbook... not an arb.

For a true arb, you need the total implied probability across platforms to be under 100%. Use our arbitrage calculator to check the numbers before placing any bets.

Multi-outcome market arbs

Some prediction markets have multiple outcomes (e.g., "Who will win the 2028 presidential election?" with 5+ candidates). When the sum of the cheapest "yes" prices across platforms for all possible outcomes is less than $1, you have a multi-way arbitrage.

This requires buying each outcome's "yes" shares on whichever platform offers the lowest price. The math gets more complex, but the principle is identical.

Where to find prediction market arbs

Manual scanning

Check the same market across platforms daily. Focus on:

• High-volume markets: More liquidity means you can actually execute at the listed price
• Markets nearing resolution: Prices converge as the event approaches, but gaps can persist until the last hours
• New markets: When a market first launches on a second platform, the initial pricing often diverges from established prices elsewhere

Automated tools

Several tools track cross-platform prices:

• Bet Hero flags arbitrage opportunities across sportsbooks and can catch overlaps with prediction market pricing on sports outcomes
• Dedicated prediction market aggregators compare prices across Polymarket, Kalshi, and others
• Custom scripts using platform APIs (Polymarket's API is public, Kalshi offers an API for approved users)

Practical considerations

Fees eat into margins

Every platform charges fees. Factor these into your arb calculation:

PredictIt's 10% combined fee structure makes it difficult to arb profitably. Polymarket and Kalshi have much lower friction.

Capital lock-up

Unlike sports bets that resolve in hours, prediction market positions can be open for weeks or months. Your capital is locked until the market resolves or you sell your position. A 4% arb over 3 months is a 16% annualized return, which is solid. A 4% arb over 12 months is just 4%, which may not justify the capital lock-up and counterparty risk.

Calculate annualized returns before committing capital to longer-dated markets.

Resolution risk

Prediction markets can resolve ambiguously. If a question is poorly worded, different platforms might resolve the same event differently. One platform rules "Yes," another rules "No," and your "guaranteed" arb becomes a guaranteed loss.

Before arbing, read the resolution criteria on both platforms. If there's any ambiguity in how the outcome will be determined, skip it. This is especially common with political and cultural markets where edge cases arise.

Regulatory and platform risk

Polymarket restricts US users (though enforcement varies). Kalshi is US-regulated but has limited market selection. PredictIt is winding down some markets. There's also real platform risk: a platform could freeze withdrawals, change rules, or shut down entirely. Factor this into position sizing.

Never put your entire bankroll on a single platform. Spread capital across platforms proportional to your trust in their stability.

Prediction market arb vs. sports betting arb

The biggest advantage of prediction market arbitrage is that platforms rarely limit winning accounts. In sports betting, consistent arbing gets you limited or banned quickly. Prediction markets generally welcome all traders because more volume improves their markets.

The tradeoff is slower capital turnover and lower liquidity.

Getting started

1. Fund accounts on 2-3 platforms. Start with Polymarket and Kalshi for the best combination of market overlap and low fees.

2. Identify overlapping markets. Look for identical or near-identical questions across platforms. Political and economic markets have the most overlap currently.

3. Calculate the arb. Use our arbitrage calculator with the implied probabilities from each platform. Total implied probability under 100% = arb exists.

4. Check liquidity. Verify you can actually execute at the listed prices with meaningful size. Thin order books kill arb margins.

5. Read resolution criteria. Make absolutely sure both platforms will resolve the market the same way. When in doubt, skip it.

6. Execute simultaneously. Buy on both platforms as close to the same time as possible. Prices can shift between your first and second trade.

7. Track everything. Log your positions, costs, fees, and returns. Use our free bet tracker to monitor your sports-side positions alongside prediction market arbs.

For a deeper understanding of how prediction markets work and how they relate to sports betting, read our complete guide to prediction markets.