How Betting Odds Work — From Probability to Arbitrage Strategy
Understand how odds work on Bet365, the three formats (decimal, fractional and American), how they reflect probability, and how to spot a sure bet using the arbitrage strategy.
Odds in betting represent the probability of an outcome occurring and determine how much you can win from a wager. Understanding how they work is the first step to betting smarter — and spotting the rare opportunities where the math works in your favour.
What odds actually represent
Odds serve two purposes at once: they indicate the likelihood of an event happening, and they determine your potential payout if you win.
Lower odds mean the bookmaker considers the outcome more likely — so the payout is smaller. Higher odds mean the outcome is considered less likely — so the payout is bigger. This relationship is the foundation of everything that follows.
Odds formats on Bet365
Bet365 supports three formats. You can switch between them in your account settings.
Decimal odds (most common globally)
Displayed as numbers like 2.50, 1.80, 3.00. Your total return equals your stake multiplied by the odds — the profit is the return minus your original stake.
Example: £10 bet at 2.50 odds = £25 total return (£15 profit + £10 stake back).
Fractional odds (traditional UK format)
Displayed as fractions like 3/2, 4/1, 1/2. The fraction shows your profit relative to your stake — the denominator is what you stake, the numerator is what you win.
Example: 3/2 odds mean you win £3 profit for every £2 staked (plus your £2 back, so £5 total return).
American odds
Positive numbers like +150 show the profit on a $100 bet. Negative numbers like -200 show how much you need to stake to win $100.
Example: +150 means a $100 bet returns $250 total ($150 profit). -200 means you stake $200 to win $100 profit ($300 total return).
How odds reflect probability
For decimal odds, the implied probability is straightforward:
Implied probability = 1 ÷ odds × 100
| Decimal odds | Implied probability | Meaning |
|---|---|---|
| 1.50 | 66.7% | Strong favourite |
| 2.00 | 50.0% | Evenly matched |
| 3.00 | 33.3% | Mild underdog |
| 4.00 | 25.0% | Underdog |
| 10.00 | 10.0% | Heavy underdog |
Bet365 specific features
The arbitrage strategy — sure bets
You’re describing an arbitrage betting strategy (also called arbing or sure betting). The idea: stake on all possible outcomes of an event such that you’re guaranteed to at least break even — or profit — regardless of the result.
For a football match with three outcomes (Team A wins, Draw, Team B wins), the minimum condition is:
The maths behind it
With £1 on each outcome at exactly 3.00 odds:
| Outcome | Your stake | Odds | Return | Net result |
|---|---|---|---|---|
| Team A wins | £1 | 3.00 | £3 | £0 profit |
| Draw | £1 | 3.00 | £3 | £0 profit |
| Team B wins | £1 | 3.00 | £3 | £0 profit |
| Total | £3 | — | £3 | £0 minimum |
If any of the outcomes has odds above 3.00, you pocket the difference. For example, if Team A is priced at 3.50:
- Total stake: £3
- Return if Team A wins: £3.50
- Net profit: £0.50
What to look for on Bet365
Search for matches where all three 1X2 markets show odds of 3.00 or higher simultaneously. This typically occurs in:
- Very evenly matched games where the bookmaker is genuinely uncertain
- Lower-league matches between similarly-ranked teams
- Cup matches between teams from different divisions
- Early-season fixtures with little form data available
Practical recommendations
The key takeaway
Odds are a bookmaker's representation of probability, with a built-in margin. Understanding the maths — 1 ÷ odds × 100 for implied probability, stake × odds for decimal returns — gives you the tools to evaluate any bet rationally.
The arbitrage strategy is mathematically sound: when all three outcomes in a 1X2 market offer odds of 3.00 or higher, you can guarantee no loss. The challenge is finding those opportunities — they're rare on a single platform but more achievable when you compare prices across multiple bookmakers.
The moment you spot all three outcomes at 3.00 or above simultaneously, you've found a guaranteed profit opportunity. The clock is ticking to act on it.
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