How to read odds and understand their probability?

Introduction: The Foundation of All Betting

Knowing how to read odds and understand the probability they represent is the fundamental skill of every bettor. Without this mastery, it’s impossible to evaluate whether a bet is worth placing.

This comprehensive guide will teach you to decode all odds formats and instantly calculate the associated probabilities.

The 3 Odds Formats Explained

<img src=”formats-cotes-decimales-fractionnelles-americaines.jpg” alt=”Comparison of three odds formats: decimal, fractional, American” title=”How to read different sports betting odds formats” width=”800″ height=”450″ />

1. Decimal Odds (European)

The simplest format and most widely used in France and Europe.

Reading: The number indicates how much you get back for €1 bet

Examples:

• Odds 2.00 = Get back €2 for €1 bet
• Odds 1.50 = Get back €1.50 for €1 bet
• Odds 3.75 = Get back €3.75 for €1 bet

Winnings calculation:

Total returns = Stake × Odds
Net profit = (Stake × Odds) - Stake

2. Fractional Odds (British)

Traditional format in the United Kingdom and Ireland.

Reading: Fraction indicating profit relative to stake

Examples:

• 1/1 (evens) = Profit of €1 for €1 bet
• 2/1 = Profit of €2 for €1 bet
• 1/2 = Profit of €0.50 for €1 bet

Conversion to decimal:

Decimal odds = (Numerator/Denominator) + 1
Example: 3/2 = (3/2) + 1 = 2.50

3. American Odds (Moneyline)

Format used in the United States with + or –

Reading:

• Positive odds (+): Profit for a $100 stake
• Negative odds (-): Stake needed to win $100

Examples:

• +200 = Win $200 for $100 staked
• -150 = Stake $150 to win $100

Conversion to decimal:

• If positive: (Odds/100) + 1
• If negative: (100/|Odds|) + 1

Quick Conversion Table

How to Calculate Implied Probability

The Universal Formula

To understand the probability of decimal odds:

Probability = 1 / Odds × 100

Practical Examples

Odds 2.00:

• Calculation: 1 / 2.00 × 100 = 50%
• Interpretation: The bookmaker estimates 50% chance

Odds 1.80:

• Calculation: 1 / 1.80 × 100 = 55.56%
• Interpretation: Favorite with ~56% chance

Odds 4.50:

• Calculation: 1 / 4.50 × 100 = 22.22%
• Interpretation: Underdog with ~22% chance

Quick Mental Calculator

Tips for quick calculation:

The Bookmaker’s Margin (Overround)

Understanding Why Probabilities Exceed 100%

Bookmakers add a margin to guarantee their profit.

Tennis match example:

• Player A: 1.80 (55.56%)
• Player B: 2.10 (47.62%)
• Total: 103.18%

The margin = 103.18% – 100% = 3.18%

Calculating “True” Probabilities

To obtain real probabilities:

1. Calculate implied probabilities
2. Add them up (e.g.: 103.18%)
3. Divide each probability by this total

Example:

• Player A: 55.56% / 103.18% = 53.86%
• Player B: 47.62% / 103.18% = 46.14%
• Adjusted total: 100%

Reading Odds on Different Markets

Match 1X2 (Football)

Example Real Madrid vs Barcelona:

• 1 (Real): 2.40 → 41.67%
• X (Draw): 3.30 → 30.30%
• 2 (Barça): 3.00 → 33.33%
• Total: 105.30% (margin 5.30%)

Interpretation: Real slightly favored at home

Over/Under Goals

Example Over/Under 2.5 goals:

• Over 2.5: 1.85 → 54.05%
• Under 2.5: 2.05 → 48.78%
• Total: 102.83% (margin 2.83%)

Interpretation: Rather offensive match expected

Asian Handicap

Example handicap -0.5:

• PSG -0.5: 1.95 → 51.28%
• Lyon +0.5: 1.95 → 51.28%
• Total: 102.56% (margin 2.56%)

Note: Margin often lower on handicaps

Using Probabilities to Identify Value

The Value Bet Concept

A bet has value when your estimate exceeds the implied probability.

Formula: Value = (Your probability × Odds) – 1

Practical Example

Match: Marseille vs Nice

• Marseille odds: 2.30 (43.48%)
• Your analysis: 50% chance for Marseille

Value calculation:

• Value = (0.50 × 2.30) – 1 = 0.15
• +15% value = Good bet!

Quick Identification Table

Odds Movements and Their Meaning

Dropping Odds = Rising Probability

Example:

• Opening: PSG at 1.80
• Now: PSG at 1.65
• Interpretation: Many betting on PSG

Possible reasons:

• Opponent injury
• Favorable team lineup
• Sharp money
• Media effect

Rising Odds = Falling Probability

Example:

• Opening: Lyon at 3.00
• Now: Lyon at 3.50
• Interpretation: Low confidence in Lyon

Implications:

• Possible value appeared
• Negative information emerged
• Bet balancing

Practical Applications by Level

For Beginners

Focus on:

1. Master decimal odds only
2. Memorize key probabilities (1.50, 2.00, 3.00)
3. Use the rule: “Odds 2.00 = 50/50”
4. Avoid odds < 1.30 or > 5.00

Exercise: Convert 10 odds per day to probabilities

For Intermediate Players

Deepen your knowledge:

1. Systematically calculate margins
2. Compare at least 3 bookmakers
3. Track odds movements
4. Identify low margin markets

Tool: Create an automatic conversion Excel sheet

For Advanced Players

Optimize:

1. Exploit opening odds
2. Calculate your own lines
3. Arbitrage between formats
4. Model probabilities

Common Mistakes to Avoid

❌ Mistake 1: Confusing Odds and Probability

Wrong: “Odds 3.00 = 30% chance” Right: “Odds 3.00 = 33.33% chance”

❌ Mistake 2: Ignoring the Margin

Wrong: “Odds reflect true chances” Right: “Odds include 3-8% margin”

❌ Mistake 3: Preferring High Odds

Wrong: “Odds 10.00 = easy big wins” Right: “Odds 10.00 = only 10% chance”

❌ Mistake 4: Not Comparing

Wrong: “All odds are equal” Right: “15-20% difference possible between bookmakers”

Quick Reference Guide

Favorite Odds (< 2.00)

• 1.20 → 83%: Ultra-favorite
• 1.50 → 67%: Clear favorite
• 1.80 → 56%: Slight favorite

Balanced Odds (2.00 – 3.00)

• 2.00 → 50%: 50/50
• 2.50 → 40%: Slight underdog
• 3.00 → 33%: Underdog

Underdog Odds (> 3.00)

• 4.00 → 25%: Clear underdog
• 6.00 → 17%: Big surprise
• 10.00 → 10%: Miracle

Practice Quiz

Test yourself:

1. Odds 1.75 = ?% probability
2. 60% chance = odds of ?
3. Odds 1.90/1.90, margin = ?%
4. Value if odds 2.80 and you estimate 40%?

Answers:

1. 57.14%
2. 1.67
3. 5.26%
4. +12% value

Conclusion: Mastering Odds, Key to Success

Correctly reading odds and understanding their probability is the foundation of all intelligent betting. This skill will allow you to:

✅ Quickly identify value ✅ Effectively compare bookmakers ✅ Avoid low expectation bets ✅ Progress toward profitability

Practice these conversions daily until they become automatic. It’s an investment that will pay off on all your future bets.

Train with Talacote! Our odds converter and probability calculator helps you master all formats instantly.