Strategy

Prediction Market Arbitrage: Finding Gaps Between Kalshi and Polymarket

When two prediction markets price the same event differently, one of them is wrong — and that gap is money on the table. Cross-platform prediction market arbitrage is one of the most underexploited strategies in modern trading because it requires monitoring both Kalshi and Polymarket simultaneously, and most traders only use one.

This guide explains how prediction market arbitrage works, where to find opportunities, and what risks to manage.

How Prediction Market Arbitrage Works

Prediction markets price outcomes as contracts between $0 and $1. If you buy "Yes" on "BTC above $100K by December" at $0.45, you're paying 45 cents for a contract that pays $1 if the event happens and $0 if it doesn't. The price implies a 45% probability.

Arbitrage arises when the same event has different prices on different platforms:

This is pure arbitrage — a risk-free profit. In practice, pure arbitrage is rare and gets closed quickly. More common are statistical arbitrage opportunities where the gap is smaller but persistent.

Types of Prediction Market Discrepancies

1. Pure Arbitrage (YES + NO < $1)

When the YES price on one platform plus the NO price on another totals less than $1, it's a guaranteed profit. These are rare and short-lived because automated market makers close them quickly.

2. Statistical Arbitrage (Persistent Price Gaps)

More commonly, the same event trades at different probabilities on each platform. For example, Kalshi might price "Fed rate cut in June" at 35% while Polymarket prices it at 42%. The 7-point gap reflects different user bases and information — not necessarily an arbitrage.

The strategy: take a directional view on who's right. If your analysis supports Kalshi's lower probability, buy NO on Polymarket (which is cheap relative to the signal). If your analysis supports Polymarket, buy YES on Kalshi (cheap there).

3. Timing Arbitrage

News and information propagate at different speeds to different platforms. Kalshi users tend to be US-based and react to US market hours news faster. Polymarket users are global and crypto-native — they react to crypto-specific news faster. During breaking events, the platform that reacts first moves price first, creating a brief window to trade the lagging platform.

Where Discrepancies Are Largest

Category	Typical Gap	Why
Crypto events	5-15 cents	Polymarket has crypto-native users with better info. Kalshi users are less crypto-savvy.
US politics	3-8 cents	Kalshi has US users closer to the info. Polymarket has offshore users with different biases.
Economics (Fed, CPI)	2-5 cents	Kalshi's institutional users price these well. Smaller gaps.
Sports	1-3 cents	Well-arbitraged by traditional sports bettors. Least opportunity.
Niche events	5-20 cents	Low liquidity on both platforms = wide spreads = largest opportunities.

Step-by-Step: Finding Arbitrage Opportunities

1. Identify shared events. Both Kalshi and Polymarket must offer markets on the same event with the same resolution criteria. Watch for subtle differences in how they define "above $100K" (end-of-day vs. any point during the day).
2. Compare prices. Check the YES price on both platforms. A gap of 5+ cents is worth analyzing. Under 3 cents is usually consumed by fees and spreads.
3. Verify resolution criteria match. This is critical. "BTC above $100K by December 31" could mean: closing price on Dec 31, any time before Dec 31, or average price on Dec 31. If the criteria differ, it's not the same bet and comparing prices is misleading.
4. Calculate net profit after fees. Kalshi charges $0.01/contract. Polymarket has no fee but you pay the spread and crypto gas costs. Factor these into your calculation.
5. Execute on both platforms. Ideally simultaneously. Price gaps can close within minutes.
6. Wait for resolution. One side pays out. Collect your profit.

Risks and Limitations

Using Fred Intelligence for Arbitrage Detection

Fred Intelligence tracks prices on both Kalshi and Polymarket daily across all shared categories. Our Prediction Market Cheat Sheet highlights:

• Cross-platform price comparison for identical or near-identical events
• Gap alerts when discrepancies exceed 5 cents
• Resolution criteria comparison to flag potential criteria mismatches
• Historical gap analysis showing which categories consistently produce the largest discrepancies
• Volume and liquidity data so you know whether the gap is tradeable or just theoretical

Is Prediction Market Arbitrage Worth It?

For most retail traders, statistical arbitrage (taking a directional view informed by cross-platform discrepancies) is more practical than pure arbitrage. The gaps are bigger, the capital requirements are lower, and you don't need simultaneous execution.

For larger accounts ($10K+), pure arbitrage on major events can produce meaningful risk-adjusted returns, especially during high-volatility periods when gaps widen.

Either way, monitoring both platforms gives you better information than monitoring one — even if you never execute a formal arbitrage trade. Seeing where the platforms disagree tells you where uncertainty is highest, which is valuable context for any trading decision.