Is arbitrage really risk-free?

The arithmetic is. The execution is not. Lines move between legs, stakes get cut below what you asked for, one leg can void while the other stands, and books restrict accounts that only bet stale prices. Call it low-risk rather than risk-free.

What sums do I actually see?

Genuine arbitrages are usually between 0.5% and 2%. Anything above about 5% is nearly always a mistake somewhere — different lines, different periods, a stale price that will be voided, or a market one book has already taken down.

Why does cent rounding matter?

Because on a 1% arb the ideal split runs to fractions of a cent and books only take round amounts. The rounded figure is what you would actually be paid, and on a thin arb it can be the difference between a profit and a loss.

Will I get limited for doing this?

Very likely, eventually. Betting only into prices that are about to move is the easiest pattern for a sportsbook to detect, and the usual response is to cut stakes to a few dollars rather than to close the account.

What happens if one leg is voided?

You are left holding a naked bet on the other side. Void rules differ between books — postponements, withdrawn players and dead heats are the usual culprits — so check both before assuming every outcome settles.

Arbitrage Calculator

Enter every outcome's best price. If they sum to less than 100%, this splits your stake so you win the same amount whatever happens.

Total to stake

Split across every outcome so all of them return the same.

Guaranteed profit

$37.35

The market prices at 96.40% — below 100%, so covering every outcome returns $1,037.35 whichever one lands. That is 3.73% on the money staked, before anything in the real world goes wrong.

Market total: 96.400%
Return on any outcome: $1,037.35
Profit: +$37.35
ROI: 3.73%
After cent rounding: +$37.34

Stake per outcome and what each one returns
Outcome	Decimal	Stake	Rounded	Returns	Profit
Book A — side 1	2.100	$493.98	$493.98	$1,037.36	+$37.36
Book B — side 2	2.050	$506.02	$506.02	$1,037.34	+$37.34

A price on a screen is not a bet in an account. Arbitrages are usually thin, short-lived and priced by one book being slow — so the second leg can move before you place it, the stake can be cut to a fraction of what you asked for, and books that notice the pattern limit the account. Treat the figure above as the best case, and check both books’ void rules before assuming every outcome settles.

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What is arbitrage betting?

Arbitrage betting — arbing, or a surebet — means backing every outcome of an event across different sportsbooks at prices that together guarantee a profit whichever result lands.

It exists because books price independently and disagree. When the best price on each side comes from a different place and the implied probabilities add to less than 100%, covering the whole market returns more than it costs.

The margins are thin — typically under 2% — and the arithmetic is the easy half. Lines move between placing the legs, stakes get cut, and books restrict accounts that only ever bet stale prices.

How it works

An arbitrage exists when different books price the same event so generously between them that backing every outcome returns more than it costs. The test is a single number: add up the implied probability of every side, and if the total comes to less than 100% there is money in it.

That total is what a bookmaker’s margin normally pushes above 100%. A −110 both-ways market sums to 104.8%, and the 4.8% is the book’s. An arbitrage is what happens when two books disagree enough that the best price on each side, taken from different places, sums below 100 — usually because one of them has been slow to move.

The stake split follows from wanting every outcome to return the same amount: each side gets a share proportional to its own implied probability. Then the return is the same figure whichever way it goes, and the profit is that figure minus what you put in.

What the arithmetic cannot tell you is whether the bet is placeable. Arbitrages are typically under 2%, which means a small line move between placing the first leg and the second wipes out the entire edge — and leaves you holding a one-sided bet you never wanted. Stakes get cut. Accounts that only ever bet stale prices get limited quickly. And if one leg voids while the other stands, you are exposed on the remainder. The after cent rounding figure is there because on a thin arb, even rounding to placeable amounts can take the profit away.

The formula

market total = Σ (1 / decimalᵢ)

arbitrage exists  ⟺  market total < 1

stakeᵢ  = total × (1/decimalᵢ) / market total
return  = total / market total          (identical for every outcome)
profit  = return − total
ROI     = profit / total

The same allocation the dutching calculator uses. Arbitrage is dutching a market that happens to price below 100%.

A worked example

Book A has one side at +110 (2.10) and Book B has the other at +105 (2.05). Implied probabilities are 47.62% and 48.78%, summing to 96.40% — an arbitrage.

Staking $1,000: $494 goes on the +110 and $506 on the +105. Either way you get back $1,037.35, for a profit of $37.35 — 3.73% on the money, locked.

Now watch what a small move does. If the +110 drops to +102 before you place it, the market sums to 100.4% and the position loses about $4. The whole edge was eight cents of line, and that is the normal case rather than bad luck.

Common questions

Is arbitrage really risk-free?: The arithmetic is. The execution is not. Lines move between legs, stakes get cut below what you asked for, one leg can void while the other stands, and books restrict accounts that only bet stale prices. Call it low-risk rather than risk-free.
What sums do I actually see?: Genuine arbitrages are usually between 0.5% and 2%. Anything above about 5% is nearly always a mistake somewhere — different lines, different periods, a stale price that will be voided, or a market one book has already taken down.
Why does cent rounding matter?: Because on a 1% arb the ideal split runs to fractions of a cent and books only take round amounts. The rounded figure is what you would actually be paid, and on a thin arb it can be the difference between a profit and a loss.
Will I get limited for doing this?: Very likely, eventually. Betting only into prices that are about to move is the easiest pattern for a sportsbook to detect, and the usual response is to cut stakes to a few dollars rather than to close the account.
What happens if one leg is voided?: You are left holding a naked bet on the other side. Void rules differ between books — postponements, withdrawn players and dead heats are the usual culprits — so check both before assuming every outcome settles.

The guide behind this calculator

Arbitrage, Hedging and MiddlesThree ways to bet both sides — one locks in profit, one locks in certainty, one buys a window where both bets win.11 min read

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For informational and analytical purposes only. These tools do not predict outcomes and do not recommend wagers.