Beginner📖 10 min read

Understanding Betting Odds

Master the fundamentals of betting odds. Learn how to read different formats, calculate probabilities, and identify value opportunities in the betting markets.

What Are Betting Odds?

Betting odds represent two key pieces of information: the probability of an outcome occurring and how much money you can win if your bet is successful. They are the foundation of all sports betting and understanding them is crucial for making informed decisions.

Odds are set by bookmakers based on their assessment of how likely an event is to happen, plus a built-in profit margin (called the "overround" or "vig"). This means odds don't just reflect true probability – they also include the bookmaker's edge.

Key Concept

Lower odds = Higher probability = Lower potential winnings
Higher odds = Lower probability = Higher potential winnings

Decimal Odds (European Format)

Decimal odds are the most common format worldwide and the easiest to understand. They show your total return (stake + profit) for every unit wagered.

How Decimal Odds Work
Formula: Total Return = Stake × Decimal Odds
Profit: Total Return - Stake
Example 1: £10 bet at 2.50 odds
Total Return = £10 × 2.50 = £25
Profit = £25 - £10 = £15
Example 2: £20 bet at 1.75 odds
Total Return = £20 × 1.75 = £35
Profit = £35 - £20 = £15
Example 3: £5 bet at 4.00 odds
Total Return = £5 × 4.00 = £20
Profit = £20 - £5 = £15
1.50
Strong Favorite
66.7% implied probability
2.00
Even Money
50% implied probability
4.00
Underdog
25% implied probability

Fractional Odds (UK Format)

Fractional odds show the profit you'll make relative to your stake. They're traditionally used in the UK and Ireland, especially for horse racing.

How Fractional Odds Work
Format: Profit/Stake (e.g., 3/1, 5/2, 1/4)
Reading: "3 to 1" means you win £3 for every £1 staked
3/1 odds: £10 stake
Profit = £10 × (3/1) = £30
Total Return = £30 + £10 = £40
5/2 odds: £10 stake
Profit = £10 × (5/2) = £25
Total Return = £25 + £10 = £35
1/4 odds: £10 stake
Profit = £10 × (1/4) = £2.50
Total Return = £2.50 + £10 = £12.50
Converting Fractional to Decimal
Formula: Decimal Odds = (Numerator ÷ Denominator) + 1
3/1 = (3 ÷ 1) + 1 = 4.00
5/2 = (5 ÷ 2) + 1 = 3.50
1/4 = (1 ÷ 4) + 1 = 1.25

American Odds (Moneyline)

American odds use positive and negative numbers to show favorites and underdogs. They're primarily used in the United States for sports betting.

Positive Odds (+)
Underdogs - shows profit on $100 stake
+200: Win $200 profit on $100 stake
Total return: $300
+150: Win $150 profit on $100 stake
Total return: $250
Negative Odds (-)
Favorites - shows stake needed to win $100
-200: Stake $200 to win $100 profit
Total return: $300
-150: Stake $150 to win $100 profit
Total return: $250

Implied Probability

Implied probability converts odds into a percentage, showing what the bookmaker believes is the likelihood of an outcome occurring.

Calculating Implied Probability
Formula: Implied Probability = (1 ÷ Decimal Odds) × 100
1.50 odds
(1 ÷ 1.50) × 100 = 66.7%
2.00 odds
(1 ÷ 2.00) × 100 = 50%
4.00 odds
(1 ÷ 4.00) × 100 = 25%

Finding Value Bets

A value bet occurs when you believe the true probability of an outcome is higher than what the odds suggest. This is the key to long-term profitable betting.

Value Betting Example
Scenario: Manchester City vs Brighton
Bookmaker odds for City win: 1.80 (55.6% implied probability)
Your assessment: City has a 65% chance of winning
This is a value bet!
Your assessment (65%) is higher than the implied probability (55.6%), suggesting the odds offer value.
Important Note

Value betting requires accurate assessment of probabilities, which comes with experience, research, and statistical analysis. Even value bets can lose – the goal is long-term profitability.

Quick Reference Guide

Common Odds Conversions
DecimalFractionalProbability

1.251/480%
1.501/266.7%
2.001/150%
3.002/133.3%
4.003/125%
Key Takeaways
  • • Lower odds = higher probability, lower winnings
  • • Higher odds = lower probability, higher winnings
  • • Decimal odds show total return per unit staked
  • • Implied probability helps assess value
  • • Value betting is key to long-term success
  • • Always consider the bookmaker's margin