Arbitrage Calculator: Understanding Margin From the Other Side

An arbitrage calculator takes two prices on opposite outcomes and tells you whether backing both guarantees a profit, how to split the stake, and what the return is either way.

The test is simple: add the implied probabilities. Below 100% and an arbitrage exists, because the two bookmakers together have priced the event at less than certainty. That gap is your guaranteed return, and it is usually very small.

The practical obstacles are what stop this being a business. Opportunities are brief, prices move while you are placing the second leg, stakes get limited quickly on accounts that only ever take arbs, and a voided leg turns a guaranteed profit into an unhedged loss. Treat the calculator as the clearest available illustration of how margin works, which is genuinely valuable, rather than as a strategy.

Key points

Combined implied probability below 100% means an arb exists
Returns are small and windows are brief
Accounts that only take arbs get limited quickly
A voided leg converts a sure thing into an open position

Frequently asked

Is arbitrage betting legal?

It is generally lawful where betting itself is lawful, but bookmakers restrict accounts that do it, which is a commercial matter rather than a legal one.

How much can you make?

Typically very small percentages per opportunity, which is why it requires large stakes and many accounts to matter.

Why is it hard in practice?

Prices move between placing the two legs, limits arrive quickly, and a voided leg leaves you exposed on one side.

Put it to use

Arbitrage Calculator: Understanding Margin From the Other Side

Key points

Frequently asked

Put it to use

Read next