Betting odds are displayed in different formats depending on region and platform.
The three most common formats are:
Decimal
Fractional
American (Moneyline)
Understanding how to convert between them ensures you can accurately compare prices and calculate implied probability.
Decimal Odds
Decimal odds show total return per unit staked.
Example:
2.50
This means:
1 unit stake returns 2.50 total (1.50 profit).
Decimal odds are the simplest for probability conversion.
Implied Probability = 1 ÷ Decimal Odds × 100
Fractional Odds
Fractional odds show profit relative to stake.
Example:
3/2
This means:
For every 2 units staked, you profit 3 units.
To convert fractional to decimal:
Decimal = (Fractional numerator ÷ denominator) + 1
Example:
3/2 → (3 ÷ 2) + 1 = 2.50
American (Moneyline) Odds
American odds are expressed as positive or negative numbers.
Positive (+150)
Negative (-200)
Positive American Odds
+150 means:
Bet 100 to win 150.
To convert to decimal:
Decimal = (American ÷ 100) + 1
+150 → (150 ÷ 100) + 1 = 2.50
Negative American Odds
-200 means:
Bet 200 to win 100.
To convert to decimal:
Decimal = (100 ÷ |American|) + 1
-200 → (100 ÷ 200) + 1 = 1.50
Quick Reference Examples
Decimal 2.00
Fractional 1/1
American +100
Implied Probability 50%
Decimal 1.50
Fractional 1/2
American -200
Implied Probability 66.67%
Decimal 3.00
Fractional 2/1
American +200
Implied Probability 33.33%
Why Conversion Matters
If you cannot convert formats:
You may misjudge price differences.
You may overlook better odds at another bookmaker.
You may miscalculate implied probability.
Price precision determines value.
The Professional Standard
Disciplined bettors:
Convert odds quickly between formats.
Think in decimal for calculation clarity.
Always translate into implied probability before evaluating value.
Understanding format differences prevents confusion and protects edge.
Core Principles
Decimal shows total return per unit.
Fractional shows profit relative to stake.
American shows profit relative to 100 units.
All formats represent the same probability.
Always convert to implied probability for value assessment.
