SlateProof

Arbitrage calculator for sportsbooks and exchanges

Updated

Enter every outcome’s price and a total stake to get exact stakes, what each outcome pays and the profit left after exchange fees and rounding. It handles two or three outcomes and says so when there is no arbitrage.

Outcomes
Round stakes to
Outcome 1

For example +106, 2.06 or 49 (cents).

Outcome 2
Prices are examples, not live odds.

Worst-case profit

$12.04

2.41% on the $500 you stake, if every bet is accepted at these prices.

OutcomeBet atStakePays if it wins
Outcome 1Any sportsbook+106 · 2.06$249$512.94+$12.94 profit
Outcome 2Any sportsbook+104 · 2.04$251$512.04+$12.04 profit
Total staked
$500
Payout range
$512.04 to $512.94
Return on stake
2.41%
Profit with exact stakes
$12.49
Prices add up to
97.56%
  • Rounding to whole dollars costs $0.45 against exact stakes.
  • A locked profit needs every bet accepted at these prices. A void, a limit or a price that moves first breaks it.

Prices here are examples you can change, not live odds. The live dashboard shows today’s prices. The default example is two outcomes at +106 and +104, which are decimal 2.06 and 2.04.

How do I use the arbitrage calculator?

  1. Choose two outcomes (over and under, or two teams) or three (a win, a draw and a win).
  2. For each outcome type the price you can bet at one venue, and pick its format: American such as +106, decimal such as 2.06, or an exchange contract price in cents such as 49.
  3. Pick the venue. An exchange leg gets its taker fee applied for you, and the optional depth box caps your total at what rests at that price.
  4. Set the total you want to stake and whether to round stakes to whole dollars or to cents.
  5. Read the stakes, what each outcome pays and the worst-case profit. “No arbitrage” means the prices add up to 100% or more.

Use the price on each venue’s own screen, for the same game, market, period and line. If one price is for a different line, there is no arbitrage to find.

How is an arbitrage calculated?

An arbitrage exists when the decimal prices, after fees, satisfy 1/d1 + 1/d2 < 1 (plus 1/d3 for three outcomes). Stake each outcome in proportion to 1/d and every outcome pays the same amount, which is more than the total staked.

sum    = 1/d1 + 1/d2 (+ 1/d3)         an arbitrage when sum < 1
stake_i = total x (1/d_i) / sum
payout  = total / sum                   the same on every outcome
profit  = total / sum - total           margin = 1/sum - 1

With the example above, 1/2.06 + 1/2.04 = 0.9756, a margin of 2.50%. On $500 the exact stakes are $248.78 and $251.22, and either outcome returns $512.49, a profit of $12.49. In whole dollars you stake $249 and $251; the outcomes then pay $512.94 and $512.04, so the worst case is $12.04 (2.41%).

How do exchange fees change the result?

A taker fee comes out of every contract you buy, so it shrinks the margin. The calculator turns each exchange price into an effective decimal price, the payout per dollar you actually spend, before it adds anything up.

VenueTypeFee used by the calculators
DraftKings, FanDuel, BetMGM, Fanatics, BetRivers, Hard Rock BetSportsbookNone. The margin is in the odds.
KalshiExchange7% × price × (1 − price) per $1 contract, at most about 1.75¢
Polymarket USExchange6.95% × price × (1 − price) per $1 contract, at most about 1.74¢
NovigExchangeNo taker fee on pregame sports
ProphetXExchange2% of net winnings

Fee figures checked Oct 6, 2026. Fees and rounding rules change, and your own app is the final word.

Take a Kalshi contract at 49¢ against a sportsbook price of +106 on the other side. Before fees the margin is 2.52%. The fee on one contract is 0.07 × 0.49 × 0.51 = $0.0175, so the 49¢ price behaves like decimal 1.9705, and the margin after the fee is 0.71%. Most of the apparent edge was the fee. Kalshi is reported to round its fee up to the next cent on each order, and Polymarket US documents rounding to the nearest cent with ties going to the even cent. The calculator uses the unrounded formula, the same one SlateProof’s scanner uses, so expect a few cents of difference on a small order. Find the venues on the exchanges page.

How should I round stakes?

Round to whole dollars unless that gives up too much of the profit. Whole-dollar stakes are easier to place, but they make the outcomes pay slightly different amounts, so the worst case is what counts. The calculator tries rounding every stake up and down, keeps the combination with the best worst case, and in the example above that costs $0.45 against exact stakes.

When whole dollars would give up more than a fifth of the exact profit, as on a long shot, it switches to cents, the same rule SlateProof’s dashboard uses. A +2500 price against −2200 at $500 is one case: the profit is $2.52 in cents. Exchanges trade whole contracts, so cent-level stakes there are approximate.

Does it work for three-way markets?

Yes. Choose three outcomes and enter the home win, the draw and the away win. The draw is its own outcome and needs its own bet, so a three-way arbitrage needs all three prices to add up to under 100% together. For illustration, +145, +245 and +240 at $500 add up to 99.21%, a margin of 0.79%: stakes of $205, $146, $148 return at least $502.25, a worst-case profit of $3.25.

Check the scope of each leg. Sportsbooks settle soccer on the 90-minute result, so confirm an exchange market is the 90-minute result and not “full match” with extra time. These are example prices, not live odds.

What can make an arbitrage lose money?

Anything that stops one leg from paying as expected: a bet that is voided or limited, a price that moves before the second bet, or a rule that settles differently at the two venues.

  • Stale or wrong prices. A price far better than the rest of the market is often an error, and the book can void it. SlateProof’s scanner blocks an arbitrage of 5% or more that fewer than three other books confirm.
  • Limits. A venue may accept less than you want or cancel after accepting. Place the less certain leg first.
  • A player who does not play. Sportsbooks void such a prop, but an exchange may not refund it: Kalshi is reported to settle at the last fair price and others may grade it No, so both legs can lose.
  • Postponement, overtime and ties. An exchange settles a postponed game at the last fair price rather than refunding it, an NFL tie pushes at a sportsbook but pays $0.50 per contract on an exchange, and a whole-number line may not be refunded on an exchange.
  • Depth, fees and rounding. An exchange fills only what rests at its price, and thin margins disappear into fee and contract rounding. The scanner ignores arbitrages under 0.2%, or 0.5% when a leg is at an exchange.

Betting at a licensed venue is legal where that venue operates, and arbitrage is not a crime, but sportsbooks can limit or close accounts that win consistently, and which venues you can use depends on your state. The arbitrage betting guide covers limits and terms, and the state pages show who operates where. This is not legal advice, and your venue’s own app has the final say.

Where can I find live arbitrage?

The live dashboard scans every snapshot of every tracked event across ten legal US sportsbooks and exchanges, net of the same fees, and lists each one with exact stakes and the age of its prices. A locked profit there still depends on every leg being accepted at the price shown.