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Prediction Market Arbitrage: How to Find Risk-Free Profits

Updated March 2026 — A complete guide to finding and exploiting price inefficiencies across prediction markets. Strategies, examples, tools, and common pitfalls.

1. What Is Prediction Market Arbitrage?

Arbitrage is the practice of exploiting price differences for the same asset across different markets to lock in a guaranteed profit. In prediction markets, this means finding situations where the combined cost of covering all outcomes is less than the guaranteed payout.

Because prediction markets are fragmented across multiple platforms — Polymarket, Kalshi, Robinhood, and others — the same real-world event can have different prices on different platforms. When prices diverge enough to overcome fees, an arbitrage opportunity exists.

Why Does Arbitrage Exist?

2. Types of Arbitrage Opportunities

Type Where Typical Return Difficulty
Cross-platform Same event on different platforms 1-5% Medium
Intra-market Yes + No prices on one platform 1-5% Easy
Multi-outcome Markets with 3+ outcomes 2-10% Medium
Time arbitrage Related events with timing gaps Variable Hard

3. Cross-Platform Arbitrage

The most common form of prediction market arbitrage: the same event is priced differently on two platforms.

Example: "Will the Fed cut rates in June 2026?"

Polymarket: Yes at $0.62
Kalshi: Yes at $0.56

Strategy: Buy Yes on Kalshi at $0.56, buy No on Polymarket at $0.38 (= 1 - 0.62)
Total cost: $0.56 + $0.38 = $0.94
Guaranteed payout: $1.00 (one side always wins)
Guaranteed profit: $0.06 per share = 6.4% return

How to Execute

  1. Find the same event on both Polymarket and Kalshi
  2. Check if the combined cost of covering both outcomes is less than $1.00
  3. Buy the cheaper side on each platform simultaneously
  4. Wait for resolution — one side pays $1.00, the other pays $0
  5. Net profit = $1.00 - total cost - fees

Watch Out: Resolution Risk

Markets on different platforms may have different resolution criteria. A market that resolves "Yes" on Polymarket might resolve "No" on Kalshi due to different source data or timing. Always compare the exact resolution rules before executing cross-platform arbitrage.

4. Intra-Market Arbitrage

Sometimes the Yes and No prices within a single market don't add up to $1.00. This creates a risk-free opportunity on a single platform.

Example: Mispriced binary market on Polymarket

Yes: $0.55
No: $0.40
Total: $0.55 + $0.40 = $0.95

Strategy: Buy both Yes and No for $0.95
Guaranteed payout: $1.00
Guaranteed profit: $0.05 = 5.3% return

These opportunities arise because bid-ask spreads can temporarily create gaps. They're usually small and short-lived, but they appear regularly in less liquid markets.

Why Intra-Market Arb Is Easiest

5. Multi-Outcome Arbitrage

Markets with 3+ outcomes (e.g., "Who will win the 2028 election?") are more likely to have arbitrage opportunities because pricing errors compound across more options.

Example: "2028 Presidential Election Winner" (5 candidates)

Candidate A: $0.35
Candidate B: $0.28
Candidate C: $0.15
Candidate D: $0.08
Others/Field: $0.06
Total: $0.92

Strategy: Buy all outcomes for $0.92
Guaranteed payout: $1.00 (exactly one candidate wins)
Guaranteed profit: $0.08 = 8.7% return

Multi-outcome markets on Polymarket frequently show total prices below $1.00 because each outcome has its own bid-ask spread, and the cumulative effect creates larger gaps.

Browse election markets and all markets on PredScope to find multi-outcome events where prices don't add up.

6. Tools for Finding Arbitrage

Tool What It Does Cost
PredScope Track live odds across markets. Monitor price changes in real time. Free
PredScope Calculator Check if Yes + No prices sum to less than $1.00. Calculate potential returns. Free
Manual Comparison Open the same market on Polymarket and Kalshi side by side. Free
Polymarket API Programmatic access to all market prices for automated scanning. Free
ArbBets Dedicated cross-platform arbitrage tracker. $59-299/mo

DIY Arbitrage Scanner

For technical traders, Polymarket's open API makes it possible to build your own arbitrage scanner. The PredScope API provides market data for the top 100 events, and you can compare prices programmatically against Kalshi's public pricing.

7. Risks and Pitfalls

Execution Risk

Prices can move between when you spot an opportunity and when you execute both legs. In fast-moving markets, the arbitrage gap may close before you complete both trades.

Resolution Risk

Different platforms may resolve the same event differently. Resolution criteria, data sources, and timing can vary. A "tie" on one platform might be "No" on another. Always read the fine print.

Fee Erosion

Account for all costs before executing:

Fee Impact Example:
Apparent arbitrage: 3% gross return
Polymarket spread: -0.5%
Kalshi fee on win: -3.5%
Net return: -1% (the arb doesn't exist after fees!)

Capital Lockup

Your capital is locked until the market resolves. A 5% arbitrage profit that takes 6 months to resolve is only ~10% annualized — you might earn more in a savings account. Factor in the time value of money.

Liquidity Risk

If you need to exit early (before resolution), you're subject to the bid-ask spread. In illiquid markets, this can wipe out your arbitrage profit entirely.

8. The Math Behind Arbitrage

Binary Market (Two Outcomes)

For a guaranteed profit, the sum of prices across all outcomes must be less than $1.00:

Arbitrage condition: Price(Yes) + Price(No) < $1.00
Profit per share: $1.00 - Price(Yes) - Price(No)
Return: Profit / (Price(Yes) + Price(No)) × 100%

Multi-Outcome Market (N Outcomes)

Arbitrage condition: Sum of all outcome prices < $1.00
Profit: $1.00 - Sum of all prices
Capital required: Sum of all prices × number of shares
Return: ($1.00 - Sum) / Sum × 100%

Cross-Platform Calculation

Platform A: Yes at $P_a
Platform B: No at $(1 - P_b)$, where $P_b$ is the Yes price on Platform B

Arbitrage exists when: P_a + (1 - P_b) < $1.00
Simplified: P_b > P_a (Yes is cheaper on Platform A)

Buy Yes on cheaper platform, buy No on the expensive platform.
Profit = P_b - P_a - fees

Frequently Asked Questions

How much money do I need to start arbitraging?

There's no minimum, but practical considerations matter. Most arbitrage opportunities have small margins (1-5%), so you need enough capital for the profit to be worth the effort. With $1,000, a 3% arbitrage opportunity yields $30. You'll also need accounts funded on multiple platforms, which requires capital split across platforms.

Is prediction market arbitrage risk-free?

In theory, pure arbitrage is risk-free — you're guaranteed to profit regardless of the outcome. In practice, there are execution risks (prices moving before you complete both trades), resolution risks (different resolution criteria), and platform risks (withdrawal delays, account restrictions). True risk-free arbitrage requires instant execution on both sides.

Can I automate prediction market arbitrage?

Yes. Polymarket's CLOB has an API that supports programmatic trading. You can build bots that scan for price discrepancies and execute trades automatically. However, automated arbitrage is competitive — professional market makers with faster infrastructure often capture opportunities before retail traders can act.

Are prediction market arbitrage profits taxable?

Yes. Arbitrage profits are taxable income, typically reported as capital gains. The same tax rules apply as for regular prediction market trading. See our prediction market taxes guide for full details on reporting.

How often do arbitrage opportunities appear?

Small opportunities (1-2%) appear frequently, especially in less liquid markets and during volatile news events. Larger opportunities (5%+) are rare and close quickly. Multi-outcome markets on Polymarket are the most consistent source of intra-market arbitrage because spreads compound across multiple outcomes.

Find Arbitrage Opportunities

Track live prediction market odds on PredScope. Compare prices, monitor movers, and use our calculator to check for mispricing.

Browse Live Markets Odds Calculator

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