How to Read Betting Odds

Complete guide to understanding American, Decimal, and Fractional odds formats

What Do Betting Odds Mean?

Betting odds tell you two essential things:

1. How much you can win - Your potential profit from a bet
2. The implied probability - How likely the bookmaker thinks something will happen

Odds can be displayed in three different formats:

• American odds (e.g., +150, -200) - Used in the United States
• Decimal odds (e.g., 2.50, 1.50) - Used in Europe, Australia, Canada
• Fractional odds (e.g., 3/2, 1/2) - Traditional in the UK and Ireland

All three formats represent the same information, just displayed differently. Let's break down each one.

American Odds Explained

American odds (also called moneyline odds) use positive (+) and negative (-) numbers.

Positive Odds (+)

Positive odds show how much profit you make on a $100 bet.

Calculating profit for positive odds:

Profit = (Stake × Odds) / 100

• Bet $50 at +150: ($50 × 150) / 100 = $75 profit
• Bet $20 at +200: ($20 × 200) / 100 = $40 profit

Negative Odds (-)

Negative odds show how much you must bet to win $100 profit.

Calculating profit for negative odds:

Profit = (Stake × 100) / Absolute Value of Odds

• Bet $100 at -150: ($100 × 100) / 150 = $66.67 profit
• Bet $50 at -200: ($50 × 100) / 200 = $25 profit

Common American Odds

Decimal Odds Explained

Decimal odds are the easiest to understand and calculate. They show your total return (profit + stake) for every $1 bet.

Calculating Payouts with Decimal Odds

Total Payout = Stake × Decimal Odds

Profit = (Stake × Decimal Odds) - Stake

Examples:

• Bet $50 at 3.00: $50 × 3.00 = $150 total ($100 profit)
• Bet $100 at 1.50: $100 × 1.50 = $150 total ($50 profit)
• Bet $20 at 2.10: $20 × 2.10 = $42 total ($22 profit)

Common Decimal Odds

Fractional Odds Explained

Fractional odds (like 3/1, 5/2) show profit relative to stake. They're traditional in horse racing and UK betting.

How to Read Fractional Odds

Numerator / Denominator

Profit = Stake × (Numerator / Denominator)

Examples:

• 5/1: Win $5 for every $1 bet
• 3/2: Win $3 for every $2 bet (or $1.50 per $1)
• 1/2: Win $1 for every $2 bet (or $0.50 per $1)
• Evens (1/1): Win $1 for every $1 bet

Calculating payouts:

• Bet $100 at 3/1: $100 × (3/1) = $300 profit, $400 total
• Bet $50 at 5/2: $50 × (5/2) = $125 profit, $175 total
• Bet $100 at 1/2: $100 × (1/2) = $50 profit, $150 total

Common Fractional Odds

Understanding Implied Probability

Implied probability is the likelihood of an outcome as suggested by the betting odds. It helps you understand how likely bookmakers think something is to happen.

Calculating Implied Probability

From Decimal Odds:

Implied Probability = (1 / Decimal Odds) × 100%

• 2.00 odds: (1 / 2.00) × 100% = 50%
• 3.00 odds: (1 / 3.00) × 100% = 33.3%
• 1.50 odds: (1 / 1.50) × 100% = 66.7%

From American Odds (Positive):

Implied Probability = 100 / (Odds + 100) × 100%

• +150 odds: 100 / (150 + 100) = 40%
• +200 odds: 100 / (200 + 100) = 33.3%

From American Odds (Negative):

Implied Probability = Abs(Odds) / (Abs(Odds) + 100) × 100%

• -150 odds: 150 / (150 + 100) = 60%
• -200 odds: 200 / (200 + 100) = 66.7%

Use our Implied Probability Calculator for quick conversions.

Converting Between Odds Formats

American to Decimal

Positive odds: (Odds / 100) + 1

• +150 → (150 / 100) + 1 = 2.50
• +200 → (200 / 100) + 1 = 3.00

Negative odds: (100 / Abs(Odds)) + 1

• -150 → (100 / 150) + 1 = 1.67
• -200 → (100 / 200) + 1 = 1.50

Decimal to American

If decimal ≥ 2.00: (Decimal - 1) × 100

• 2.50 → (2.50 - 1) × 100 = +150
• 3.00 → (3.00 - 1) × 100 = +200

If decimal < 2.00: -100 / (Decimal - 1)

• 1.67 → -100 / (1.67 - 1) = -150
• 1.50 → -100 / (1.50 - 1) = -200

Quick Conversion Tool

Use our Odds Converter to instantly convert between all formats.

How to Read Betting Lines

Moneyline Example

Point Spread Example

Learn more: Spread Betting Guide

Total (Over/Under) Example

Learn more: Over/Under Betting Guide

Tips for Reading Odds

1. Understand the Favorite vs Underdog

• Negative odds (-) or lower decimal (< 2.0) = Favorite
• Positive odds (+) or higher decimal (> 2.0) = Underdog

2. Calculate Before Betting

Always know your exact payout before placing a bet. Don't guess!

3. Compare Odds Across Sportsbooks

The same bet can have different odds at different books. Shopping for the best line increases profit.

4. Understand the Bookmaker's Margin

If you add up implied probabilities for all outcomes, it exceeds 100%. The excess is the bookmaker's profit margin (vig).

Learn more: What is Vig?

5. Use Odds to Find Value

Compare the implied probability to your own estimate of the true probability. If your estimate is higher, you've found a value bet.

Common Mistakes Reading Odds

❌ Mistake 1: Confusing Payout with Profit

Remember: Payout includes your stake back. Profit is what you win on top of your stake.

❌ Mistake 2: Thinking Higher Numbers Always Mean Better

In American odds, +500 pays more than +100, but in negative odds, -100 pays more than -500.

❌ Mistake 3: Mixing Up Formats

Don't confuse 2.50 decimal odds with 2/5 fractional odds. They're very different!

❌ Mistake 4: Ignoring Implied Probability

Odds aren't just about payouts - they tell you what the bookmaker thinks will happen.

Quick Reference Guide

✓ American Odds:

• Positive (+): Profit on $100 bet (underdog)
• Negative (-): Amount to bet to win $100 (favorite)
• Used in: United States

✓ Decimal Odds:

• Total return per $1 bet
• Easiest for calculations: Stake × Odds = Payout
• Used in: Europe, Australia, Canada

✓ Fractional Odds:

• Profit / Stake ratio
• Traditional format
• Used in: UK, Ireland, horse racing

✓ Key Conversions:

• Even money: +100 = 2.00 = 1/1
• -110 standard: -110 = 1.91 = 10/11
• 2-to-1: +200 = 3.00 = 2/1

FAQ: How to Read Betting Odds