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Arbitrage Calculator

Find risk-free betting opportunities by comparing odds across two outcomes. Calculate optimal stake distribution and guaranteed profit.

Outcome 1

Enter the odds for the first outcome (e.g., Team A wins).

Outcome 2

Enter the odds for the second outcome (e.g., Team B wins).

No Arbitrage

Combined implied probability ≥ 100%

Results

Guaranteed Profit

$0.00

ROI

—

Combined Prob.

100.00%

Optimal Stake Distribution

Outcome 1

$52.38

Payout

$100.00

Outcome 2

$47.62

Payout

$100.00

What Is Arbitrage Betting?

Arbitrage betting (or "arbing") exploits differences in odds between sportsbooks or prediction markets to guarantee a profit regardless of the outcome. When the combined implied probabilities of all outcomes total less than 100%, an arbitrage opportunity exists.

Risk-Free Profit

By distributing your stake optimally across outcomes, you lock in a guaranteed return no matter who wins.

Optimal Stakes

The calculator determines exactly how much to wager on each outcome to maximize your guaranteed profit.

Spot Opportunities

Compare odds from different sources — when combined implied probability drops below 100%, you've found an arb.

How Arbitrage Betting Works

The key formula checks whether the sum of implied probabilities is less than 1:

(1 / Decimal₁) + (1 / Decimal₂) < 1.00 = Arbitrage!

Example: Sportsbook A offers Team X at +150 (2.50 decimal) and Sportsbook B offers Team Y at +130 (2.30 decimal):

  • Implied prob. for Team X: 1/2.50 = 40.00%
  • Implied prob. for Team Y: 1/2.30 = 43.48%
  • Combined: 40.00% + 43.48% = 83.48% (under 100%)
  • Arbitrage edge: ~19.8% ROI

With a $100 total stake, you'd bet $52.17 on Team X and $47.83 on Team Y for a guaranteed profit of ~$19.79.

Frequently Asked Questions

Is arbitrage betting legal?

Yes, arbitrage betting is legal. However, sportsbooks may limit or close accounts that consistently exploit arbitrage opportunities. Always check local regulations.

How common are arbitrage opportunities?

True arbitrage opportunities are rare and usually short-lived. They typically arise when odds move quickly or when different sportsbooks disagree on probabilities. Prediction markets can also create arb opportunities when compared to traditional sportsbooks.

Can I use this for prediction markets?

Absolutely. Compare prediction market prices (converted to decimal odds) with sportsbook odds or other prediction market prices to find arbitrage opportunities across platforms.

What about markets with more than 2 outcomes?

This calculator handles 2-outcome markets. For 3+ outcome markets (like 1X2 in soccer), the same principle applies — the sum of all implied probabilities must be less than 100%. You'd need to calculate stakes for each outcome proportionally.

Why does the guaranteed profit seem small?

Arbitrage margins are typically 1-5%. The profit is small per bet but is risk-free. Arbers make money through volume — placing many bets over time to accumulate consistent, guaranteed returns.

The Complete Arbitrage Betting Guide for Prediction Markets and Sportsbooks

Arbitrage betting — also called arbing or surebets — is the practice of placing wagers on every possible outcome of an event across different platforms, locking in a guaranteed profit regardless of how the event resolves. It's one of the few legitimate, mathematically risk-free strategies in betting, and it's grown dramatically in popularity since the 2018 PASPA repeal opened US sports betting and the simultaneous rise of prediction markets like Polymarket and Kalshi. Wherever odds disagree across platforms, an opportunity may exist.

How arbitrage opportunities appear in real markets

Two different bookmakers, or a sportsbook and a prediction market, will frequently disagree about the probability of an event. One book might offer +110 on Team A while another offers +110 on Team B in the same matchup. Convert both to decimal odds (2.10 each), take the inverse to find implied probability (47.6% each), and add them: 95.2%. Because the combined implied probability is below 100%, you can wager on both outcomes and guarantee a profit equal to roughly the 4.8% margin. The arbitrage calculator on this page does the algebra for you and tells you exactly how much to stake on each side to equalize your return.

The math behind risk-free profit

The condition for arbitrage is simple: (1 / decimal₁) + (1 / decimal₂) < 1. The optimal stake on each outcome is proportional to the inverse of its decimal odds. Specifically, stake on outcome 1 = total bankroll × (1/decimal₁) / [(1/decimal₁) + (1/decimal₂)]. The guaranteed profit equals total bankroll × [1 − combined implied probability] / combined implied probability. For a 95% combined implied probability and $1,000 staked, you lock in roughly $52.60 of profit, no matter which side wins. The smaller the combined probability, the larger your guaranteed return.

Where to find arbitrage opportunities in 2026

The most reliable arb sources today are price discrepancies between traditional sportsbooks and prediction markets like Polymarket. Sportsbooks update slowly on political markets, election outcomes, and entertainment props — categories where Polymarket is the dominant price discovery venue. When breaking news moves Polymarket but sportsbooks haven't repriced yet, two-way arbs open for minutes or hours at a time. Similarly, Kalshi often diverges from FanDuel and DraftKings on macroeconomic markets like CPI prints and Fed rate decisions. Cross-platform monitoring tools and the QuantFox active markets dashboard help you spot these gaps as they emerge.

Risks that arbitrage bettors actually face

Arbitrage is mathematically risk-free only if every leg fills at the displayed price. In practice, three risks matter. First, slippage — by the time you place the second leg, the price may have moved against you, eroding or eliminating the edge. Second, account limits — sportsbooks aggressively limit accounts that consistently arbitrage, sometimes within days. Third, settlement disputes — if one platform voids a bet (rule disputes, postponed events, or technical errors), you're left exposed on the other side. Experienced arbers mitigate these by trading liquid markets, placing the lower-liquidity leg first, and diversifying across many books to avoid single-account concentration.

Arbitrage on Polymarket and Kalshi specifically

Prediction markets create a special class of arb because contracts are denominated in cents from 0 to 100 and YES + NO must sum to 100. If YES on a Polymarket contract trades at 48¢ while the same event trades at 55¢ NO on Kalshi, the implied probabilities are 48% and 45%, summing to 93% — a 7% arbitrage. You buy YES on Polymarket and NO on Kalshi, weighted by the inverse of each contract's price, and lock in profit. These intra-prediction-market arbs are the cleanest because both platforms are designed for binary outcomes, settlement rules are explicit, and trading fees are typically under 2% per side.

Bankroll management and execution discipline

Because arbitrage profits are typically 1-5% per opportunity, the strategy depends on volume and execution speed. Most successful arbers fund accounts on five to ten platforms simultaneously, keep working capital ready on each, and use tools to alert them when opportunities appear. Placing the legs in the right order matters: hit the lower-liquidity, faster-moving market first, then sweep the more liquid leg. Track every arb in a spreadsheet — including stake sizes, fills, and realized profit — to identify which platforms move fastest and which are most likely to limit you. Treat the bankroll as working capital that you actively rotate, not a static investment.