Arbitrage betting exploits pricing differences across sportsbooks, prediction markets like Polymarket and Kalshi, and regulated platforms to lock in guaranteed profit regardless of the outcome. This guide covers the math, fee structures, platform comparisons, settlement risk, bot architecture, and execution strategies for every major arb route — with links to every specialized resource on AgentBets.ai.
What Is Arbitrage Betting?
Arbitrage (or “arbing”) exploits pricing differences across betting platforms. When two or more books disagree on the odds for the same event by a wide enough margin, you can bet every outcome and lock in a guaranteed profit regardless of the result.
Traditional sports arb compares odds between sportsbooks — DraftKings vs. FanDuel vs. BetMGM. Cross-market arbitrage goes further: it compares pricing across entirely different platform types — sportsbooks, prediction markets like Polymarket and Kalshi, and betting exchanges. For a complete developer walkthrough, see the Sports Betting Arbitrage Bot Guide.
Why Arbs Exist
Sportsbooks and prediction markets serve different audiences, operate under different constraints, and react to information at different speeds:
| Factor | Sportsbooks | Prediction Markets |
|---|---|---|
| Participants | Recreational bettors, sports fans | Traders, analysts, quants |
| Pricing | Odds set by in-house traders/algos | Order book, supply/demand |
| Info Speed | React to sharp money in seconds | React to news, polls, models |
| Liquidity | Deep on popular sports | Deep on elections, thin on sports |
| Regulation | State gambling licenses / offshore | CFTC-regulated or crypto-native |
These structural differences mean that when news breaks, the two market types may take minutes or hours to converge. In traditional sports arb between two sportsbooks, the window is typically seconds. For a deeper comparison, see Sports Betting vs. Prediction Markets.
Scale of the Opportunity
IMDEA Research: $40M+ in Arb Profits
Research from IMDEA Networks Institute analyzed 86 million on-chain Polymarket bets during the 2024 U.S. election cycle (April 2024 – April 2025) and found traders captured over $40 million in arbitrage profits from cross-market pricing discrepancies. The top 3 arb wallets alone generated $4.2 million from 10,200+ combined bets.
This isn’t theoretical. Cross-market arb is a proven, profitable strategy at meaningful scale. The full analysis of these patterns is explored in our Cross-Market Arbitrage Guide.
The Arbitrage Math
Implied Probability & Odds Conversion
Every set of odds implies a probability. To detect arbs, you need to convert all formats to implied probability. The Odds Converter tool handles this interactively, but here’s the core math:
| Format | Example | Implied Prob Formula |
|---|---|---|
| American (+) | +180 | 100 / (odds + 100) |
| American (–) | –150 | |odds| / (|odds| + 100) |
| Decimal | 2.80 | 1 / decimal_odds |
| Polymarket $ | $0.65 | price = probability |
| Kalshi $ | $0.60 | price = probability |
For the full mathematical framework including dutching, three-way (1X2) detection, and multi-platform scanning algorithms, see Arbitrage Detection Algorithms.
Detecting an Arb: The Overround Test
Sum the implied probabilities of the best price per outcome across all platforms. If the total is below 100%, you have an arb. The gap is your margin.
Arb Detection Formula:
Arb % = 1 – (1/best_odds_A + 1/best_odds_B) → If positive, it's an arb.
Guaranteed profit = (Arb % × Total Stake) – Fees
Worked Example
Consider a Championship Winner future priced on both a sportsbook and Polymarket:
| Outcome | Platform | Price/Odds | Implied Prob |
|---|---|---|---|
| Team A Wins | BetOnline | +180 (2.80) | 35.7% |
| Team A Loses | Polymarket | $0.40 NO | 60.0% |
Total implied probability: 35.7% + 60.0% = 95.7%. That’s a 4.3% arb margin before fees. On a $1,000 total stake, that’s approximately $43 in guaranteed profit before accounting for platform fees.
For the full stake calculator and detailed math, see the Arbitrage Calculator.
The Platform Landscape
To arb effectively, you need to understand the three categories of platforms and how they differ. The Offshore vs. Regulated Sportsbooks comparison covers this in depth.
Prediction Markets
Polymarket
- How it works: Crypto-native prediction market on Polygon. Prices range $0–$1, where the price equals the market’s implied probability.
- Fees (March 2026): Dynamic taker fees up to ~1.8% at 50% probability. Varies by category: Sports ~0.75%, Crypto up to 1.8%, Politics/Finance ~1.0%, Geopolitics often fee-free.
- Strengths: Deepest liquidity on political/event markets. Full public API (CLOB + Gamma). 24/7 trading.
- For agents: Official API, Python client (py-clob-client). See the full Polymarket API Guide.
Kalshi
- How it works: CFTC-regulated U.S. exchange. Event contracts priced $0–$1 per contract, binary outcomes.
- Fees (March 2026): Per-contract fee up to $0.02, probability-weighted. Effectively 0% on many markets.
- Strengths: Regulated status, strong on economic indicators (Fed rate, CPI, GDP), growing sports coverage.
- For agents: REST + WebSocket APIs, decimal pricing as of March 2026. See the full Kalshi API Guide.
Offshore Sportsbooks
Offshore books serve US bettors from jurisdictions like Panama, Costa Rica, and Curaçao. They typically offer better odds, higher limits, and crypto-first banking. Full reviews at the Offshore Sportsbooks hub.
| Book | Rating | Vig | Limits | Crypto | Payout | Sharps? |
|---|---|---|---|---|---|---|
| BetOnline | 9.1/10 | 3–4% | $2K–$50K | 17+ coins | <24h | Tolerant |
| BookMaker | 8.5/10 | 2–3% | $5K–$50K+ | BTC, LTC+ | Same-day | Never limits |
| Bovada | 8.7/10 | 4–5% | $500–$5K | BTC, ETH+ | 24–48h | Moderate |
BookMaker: The Sharp’s Choice — Operating since 1985, BookMaker is the only major offshore book that never limits winning bettors. Reduced juice (–107/–108 vs. standard –110) and the highest limits in the offshore market make it the benchmark for professional sports bettors.
For head-to-head comparisons, see Bovada vs. BookMaker. For a full analysis of sportsbook odds quality, visit the live Vig Index (updated 3x daily).
Regulated US Sportsbooks
State-licensed operators like DraftKings, FanDuel, BetMGM, and Caesars offer legal certainty and consumer protection, but typically carry higher vig (4–8%) and aggressively limit winning bettors. Available in 38+ states plus DC. Full details at the Regulated Sportsbooks hub.
| Factor | Offshore | Regulated | Winner |
|---|---|---|---|
| Vig / Odds Quality | 2–5% | 4–8% | Offshore |
| Betting Limits | $5K–$50K+ | $500–$5K | Offshore |
| Crypto Payouts | 1–48h, 17+ coins | Limited/none | Offshore |
| Legal Certainty | Gray area | Fully licensed | Regulated |
| Consumer Protection | None | State oversight | Regulated |
| Winner Treatment | Varies (BookMaker best) | Aggressive limiting | Offshore |
| API/Automation | Unofficial tolerance | Official APIs emerging | Depends |
For the comprehensive 15-factor comparison, see Offshore vs. Regulated Sportsbooks. For the extended guide covering legality, taxes, and banking, see Offshore vs. Legal Sportsbooks.
Fee Structures & Minimum Arb Thresholds
Fees are what separate a theoretical arb from a real profit. Each platform type charges differently, and you must account for all fees before committing capital. The full fee breakdown is detailed in our Cross-Market Arbitrage Guide.
Fee Comparison (March 2026)
| Platform | Fee Model | Effective Cost |
|---|---|---|
| Polymarket | Dynamic taker fee based on probability | ~0.75% (sports) to ~1.8% (crypto at 50%) |
| Kalshi | Per-contract: up to $0.02, prob-weighted | Effectively 0% on many markets |
| Sportsbooks | Vig built into odds (overround) | 2–3% (sharp) to 5–8% (recreational) |
| Betfair Exchange | Commission on net winnings | 2–5% (volume-dependent) |
Minimum Arb Thresholds by Route
After accounting for fees on both sides, these are the minimum price gaps needed for a profitable arb:
- Sportsbook ↔ Sportsbook: ~0.5% minimum gap needed
- Sportsbook ↔ Polymarket: ~1.5–2.5% (higher due to Polymarket’s dynamic fees + sportsbook vig)
- Polymarket ↔ Kalshi: ~1.5–2.0% (both platforms’ fees combined)
- Sportsbook ↔ Kalshi: ~1.0–1.5% (Kalshi’s low fees help)
Vig Compounding Effect — At sharp offshore books (Pinnacle/BookMaker) with 2–3% vig vs. regulated books (DraftKings/FanDuel) at 4–5%, a bettor with a $50K annual handle saves $500–$1,500/year in vig alone by using offshore books. At $500K annual handle, that’s $5,000–$15,000.
Use the live Vig Index for real-time odds quality rankings, and the Vig Index Methodology for full transparency on how scores are calculated.
Types of Cross-Market Arbitrage
There are three primary arb routes, each with different mechanics, fee profiles, and risk characteristics. The Best Prediction Market Arbitrage Bots guide ranks the top tools for each.
Type 1: Cross-Platform (Polymarket ↔ Kalshi)
Both platforms price binary event contracts, but their different user bases and fee structures create persistent gaps. This is the most common prediction market arb.
- Best for: Political events, economic indicators, and any event priced on both platforms
- Typical margin: 1–4% before fees
- Window duration: Minutes to hours
- Capital lock-up: Until event resolution (days to months)
Type 2: Prediction Market ↔ Sportsbook
The highest-margin arb type. Sportsbooks and prediction markets have fundamentally different pricing mechanisms, creating larger gaps.
- Best for: U.S. elections, championship futures, awards
- Typical margin: 2–8% before fees
- Window duration: Hours to days (news-driven)
- Key risk: Settlement rule differences between platforms
Type 3: Intra-Platform
Arbitrage within a single platform’s related markets — e.g., correlated Polymarket contracts that don’t sum correctly.
- Best for: Related/correlated markets on Polymarket
- Typical margin: 0.5–2%
- Window duration: Minutes
- Capital lock-up: Shared resolution timeline
Real-World Arb Patterns
Based on the data in our Cross-Market Arbitrage Guide, these are the most common patterns:
| Pattern | Margin | Duration | Trigger |
|---|---|---|---|
| News Divergence | 3–8% | Min–Hours | Breaking news hits one market type first |
| Liquidity Gaps | 2–5% | Hours | Thin order books on one side |
| Settlement Premium | 1–3% | Persistent | Markets pricing different resolution rules |
| New Market Launch | 5–15% | Hours–Days | New market hasn’t found equilibrium |
| Time Zone Gaps | 2–4% | Hours | One market asleep while other reacts |
Building an Arb Bot: Architecture
A production arb bot follows a four-stage pipeline. The complete implementation with Python code is in the Sports Betting Arbitrage Bot Guide and the cross-market extension in the Cross-Market Arbitrage Guide. For the underlying detection math — dutching, three-way conditions, and multi-platform scanning — see Arbitrage Detection Algorithms.
The 4-Stage Pipeline
- Data Layer — Ingest real-time odds/prices from multiple sources
- Comparison Engine — Normalize prices, find best per-outcome across platforms
- Stake Calculator — Compute fee-adjusted stakes for equal profit
- Execution Engine — Place bets in parallel across platforms
Stage 1: The Data Stack
You need unified data from three source types. The Prediction Market API Reference provides a side-by-side comparison of all available APIs.
| Layer | Source | Coverage | AgentBets Guide |
|---|---|---|---|
| Sportsbooks | The Odds API (v4) | 40+ books, regulated + offshore | Vig Index |
| Polymarket | CLOB + Gamma APIs | All Polymarket markets | Polymarket Guide |
| Kalshi | REST + WebSocket | All Kalshi events | Kalshi Guide |
Event Matching Challenge
The hardest part of cross-market arb is matching the same event across platforms. A sportsbook’s “Super Bowl LXI Winner” must be mapped to Polymarket’s “Who will win Super Bowl LXI?” contract. Approaches include manual mapping for high-value events, fuzzy string matching, and category-based heuristics. The Cross-Market Arb Finder implements this with pre-mapped events and live scanning.
Execution Considerations
- Speed asymmetry: Sportsbook bets settle instantly; prediction market orders may take seconds to fill on thin books.
- Capital lock-up: Prediction market positions are locked until event resolution, which could be months away.
- Multi-leg risk: If Leg 1 fills but Leg 2 doesn’t, you have unhedged exposure. Pre-authenticated sessions and parallel execution are critical.
- Account longevity: Sportsbooks may limit arb bettors. Mix arb bets with recreational bets and vary stake sizes.
For the complete agent infrastructure stack (identity, wallets, trading, intelligence), see the Agent Betting Stack Guide.
Tools & Bots for Arb Hunting
You don’t have to build everything from scratch. The Best Prediction Market Arbitrage Bots guide ranks the top tools for 2026.
Top Arb Bots Ranked
| Bot | Price | Coverage | Speed | Best For |
|---|---|---|---|---|
| PolyArb Pro | $149–399/mo | Polymarket + Kalshi | Sub-second | Fastest detection |
| CrossMarket Agent | $500 one-time | 3-way (+ sportsbooks) | Seconds | Widest coverage |
| ArbScanner | $79–199/mo | Polymarket + Kalshi | 1–5 sec | Budget-friendly |
| SpreadHunter | $299 one-time | Intra-Polymarket | Seconds | Correlation arbs |
| OctoBot | Free (OSS) | Polymarket | Varies | Open source |
If you’d rather buy a ready-made bot than build one, see How to Buy an Arbitrage Bot for Polymarket for evaluation criteria, wallet setup, and red flags to watch for. For a free open-source option, the OpenClaw Arb Finder Skill provides a read-only arb scanner you can deploy today.
AgentBets.ai Interactive Tools
In addition to third-party bots, AgentBets.ai provides free interactive tools:
- Cross-Market Arb Finder — Live scanner comparing Polymarket, Kalshi, and sportsbook odds with fee-adjusted profit calculations.
- Arbitrage Calculator — Input odds from any two platforms and get stake splits and guaranteed profit.
- Odds Converter — Convert between American, Decimal, Fractional, and implied probability formats.
- Sportsbook Selector — Get personalized sportsbook recommendations based on your priorities.
Capital Requirements
| Arb Type | Minimum | Recommended |
|---|---|---|
| Cross-platform (PM ↔ PM) | $1K–$2K | $5K–$10K |
| Sportsbook ↔ PM | $1K+ | $5K–$20K |
| Intra-platform | $500–$2K | $2K–$5K |
| Sportsbook ↔ Sportsbook | $1K+ | $5K–$10K |
Settlement Risk & Resolution Differences
The most under-appreciated risk in cross-market arb is that platforms may resolve the same event differently. Understanding settlement rules is essential before committing capital.
How Platforms Resolve Differently
- Sportsbooks: Typically follow official league results. Graded within hours of game end.
- Polymarket: Resolution based on market-specific rules defined at creation. UMA oracle system for disputes.
- Kalshi: CFTC-regulated resolution criteria defined in event contracts. Government data sources preferred.
Resolution Mismatch Scenarios
Example: Contested Election — If a political outcome is challenged in court, a sportsbook might void the bet, Polymarket might resolve based on certification, and Kalshi might wait for official government declaration. Three platforms, three different outcomes from the same event.
Risk Mitigation
- Read the rules: Before placing any cross-market arb, read the settlement rules on both platforms for that specific event.
- Avoid ambiguous events: Stick to events with clear, binary outcomes and objective resolution criteria.
- Size appropriately: Account for the possibility that one leg resolves in your favor while the other voids.
- Diversify: Don’t put all capital into a single cross-market arb — spread across multiple uncorrelated events.
Legal Landscape & Tax Obligations
For the complete legal analysis, see Offshore vs. Legal Sportsbooks. This section summarizes the key points.
Federal Law (U.S.)
- UIGEA (2006): Targets financial institutions and payment processors that facilitate illegal gambling transactions. Does not target individual bettors.
- Wire Act (1961): Applied to operators transmitting wagers across state lines. Per 2011/2019 DOJ opinions, applies to sports betting only.
- Enforcement reality: Zero individual US bettors have been prosecuted for placing bets with offshore sportsbooks.
State Availability
As of March 2026, 12 states still lack legal online sports betting: California, Texas, Florida (court-blocked), Georgia, Minnesota, Alabama, Alaska, Hawaii, Idaho, South Carolina, Utah, and Wisconsin. In these states, offshore is the only option.
Tax Obligations
All Gambling Winnings Are Taxable — The IRS requires all gambling winnings to be reported regardless of source — offshore or regulated. Regulated books issue 1099/W-2G forms (auto-reported to IRS). Offshore books issue no tax documents; self-reporting on Schedule 1 Line 8b or Schedule C is required. Failure to report is tax evasion. Crypto deposits create additional capital gains tax events.
Prediction Market Regulation
- Kalshi: CFTC-regulated as a Designated Contract Market (DCM). Fully legal for US users. Issues tax documents.
- Polymarket: Crypto-native, not regulated by CFTC. Restricted for US users since 2022, though enforcement is limited. Offshore-adjacent regulatory posture.
The Arb Strategy Playbook
For Beginners (Capital: $1K–$5K)
- Start with the Odds Converter to learn odds math
- Use the free Cross-Market Arb Finder to spot opportunities manually
- Open accounts on Kalshi + one regulated sportsbook (DraftKings or FanDuel)
- Focus on high-overlap events: championship futures, election markets
- Target 2–4% arbs to give yourself margin for error
- Track every bet in a spreadsheet — record odds, stakes, fees, and outcomes
For Intermediate Bettors (Capital: $5K–$20K)
- Add offshore accounts (BetOnline + BookMaker) for better odds and higher limits
- Subscribe to an arb alert service like ArbScanner ($79–199/mo)
- Diversify across 3+ arb routes (sportsbook-sportsbook, sportsbook-PM, PM-PM)
- Implement quarter-Kelly staking for bankroll management
- Monitor the Vig Index daily to identify the best-odds books per sport
- Read the sharp betting strategies at the Sharp Betting hub
For Advanced / Developers (Capital: $20K+)
- Build a custom arb bot using the 4-stage architecture from the Sports Betting Arb Bot Guide
- Integrate The Odds API + Polymarket CLOB + Kalshi REST for three-way scanning
- Deploy automated execution with pre-authenticated sessions and parallel placement
- Use the Agent Betting Stack for identity, wallets, and trading infrastructure
- Consider PolyArb Pro or CrossMarket Agent for enterprise-grade detection
- Implement CLV (closing line value) tracking to measure edge persistence
For the full agent infrastructure, see the Agent Betting Stack Guide. For sharp betting techniques, visit the Sharp Betting hub.
Complete Resource Directory
Every resource referenced in this guide, organized by category.
Arbitrage Guides
- Cross-Market Arbitrage: Sportsbooks vs. Prediction Markets
- Sports Betting Arbitrage Bot: Developer Guide
- Best Prediction Market Arbitrage Bots 2026
- Arbitrage Detection Algorithms for Multi-Platform Agents
- How to Buy an Arbitrage Bot for Polymarket
- Build an OpenClaw Arb Finder Skill
Interactive Tools
Platform Guides
Sportsbook Reviews & Comparisons
- Offshore Sportsbooks Hub
- Regulated Sportsbooks Hub
- Offshore vs. Regulated Sportsbooks (15-factor)
- Offshore vs. Legal Sportsbooks (extended)
- Bovada vs. BookMaker
- Vig Index (live, updated 3x/day)
- Vig Index Methodology