Tools

Sure Bet Calculator — How to Calculate Guaranteed Profit 2026

8 min read · Updated January 2026

James Fletcher

Betting Analyst & Contributor at BetMan.app

A sure bet calculator does two things: it tells you whether an opportunity exists across a set of odds, and if it does, exactly how much to stake on each outcome to guarantee the same profit regardless of the result. Without a calculator, the maths is doable but error-prone. One wrong stake on one side eliminates the guarantee. Here's how to use one and understand what it's calculating.

The One Number That Matters — the Arb Margin

Every sure bet check starts with a single calculation: the sum of the implied probabilities. If this number is below 1.00 (or below 100%), a sure bet exists.

Arb Margin = (1 ÷ Odds on Outcome 1) + (1 ÷ Odds on Outcome 2)
If Arb Margin is less than 1.00 → Sure bet exists
Profit % = (1 − Arb Margin) × 100

1.05

No arb — bookmaker has 5% edge

0.96

Arb exists — 4% guaranteed profit

2-Way Sure Bet — Complete Example

Tennis match: Djokovic vs Alcaraz. No draw possible — two outcomes only.

Identifying the Arb

Bookmaker A — Djokovic to win2.20

Bookmaker B — Alcaraz to win2.25

Implied prob: (1÷2.20) + (1÷2.25)0.899

Arb exists?YES

Profit margin10.1%

Calculating Stakes — £1,000 Total

Stake on Djokovic (Bookie A)£506

Stake on Alcaraz (Bookie B)£494

If Djokovic wins: £506 × 2.20£1,113

If Alcaraz wins: £494 × 2.25£1,111

Guaranteed profit on £1,000~£112

Stake on Outcome X = Total Stake × (1 ÷ Odds X) ÷ Arb Margin

Djokovic stake: £1,000 × (1÷2.20) ÷ 0.899 = £506
Alcaraz stake: £1,000 × (1÷2.25) ÷ 0.899 = £494

3-Way Sure Bet — Football Example

A three-outcome football match (Win/Draw/Loss) requires three bookmakers to each offer sufficiently high odds on one outcome.

Man United vs Liverpool — 3-Way Market

Bookie A — Man United win3.40

Bookie B — Draw4.20

Bookie C — Liverpool win2.60

Arb margin: (1÷3.40)+(1÷4.20)+(1÷2.60)0.968

Sure bet exists?YES — 3.2% profit

Stakes on £1,000 Total

Stake on Man United£304

Stake on Draw£246

Stake on Liverpool£398

Return on any outcome~£1,033

Guaranteed profit~£33

What the Calculator Checks For You

BetMan's Arb Finder automates every step: enter the odds from two or three bookmakers, select 2-way or 3-way, and the tool instantly outputs: whether an arb exists, the profit percentage, and the exact stake for each outcome at your chosen total stake.

This eliminates the most common error in manual arbing — miscalculating the stake split. Off by even a few pounds and one outcome pays less than the other, meaning your "guaranteed" profit has variance.

Why Odds of 2.00/2.00 Don't Create a Sure Bet

A common question: if both outcomes are priced at 2.00, why isn't that a sure bet? Because (1÷2.00) + (1÷2.00) = 1.00 exactly — the margin is zero. There's no profit; you just get your money back. You need the combined probabilities to be below 1.00 — i.e., the odds collectively need to be longer than the market's fair value.

Limits and Practical Constraints

Maximum stake limits. If Bookmaker A limits you to £200 on a market, your total arb stake is capped. The profit percentage doesn't change, but the absolute amount is limited.

Odds movement. Place one side of an arb, and the other bookmaker may move their price before you've placed the second bet. This is the biggest execution risk. Always place the higher-odds, less liquid side first.

Account restrictions. Sure bettors are identified and restricted by bookmakers faster than most bettor types. The strategy has a finite lifespan per account — factor this into long-term planning.