Odds converter — decimal, fractional, American & implied probability
This tool converts betting odds between the three formats used by Australian and international bookmakers — decimal (e.g. $2.50), fractional (e.g. 6/4) and American (e.g. +150 or -200) — and shows the implied probability behind each price. Enter a price in any one format and the other two, plus implied probability, are calculated live.
The formula
Decimal is the pivot format. Fractional → decimal: decimal = (numerator ÷ denominator) + 1. American (positive) → decimal: decimal = (American ÷ 100) + 1. American (negative) → decimal: decimal = (100 ÷ |American|) + 1. Implied probability = 1 ÷ decimal odds, shown as a percentage.
Try it
Enter a valid odds value for the selected format.
Decimal
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Fractional
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American
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Implied probability
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Why odds formats differ
Australian bookmakers (TAB, Sportsbet, Bet365, Ladbrokes, Betfair AU) display decimal odds as standard — the total return per $1 staked, including your stake. UK-facing sites often use fractional odds, and US sportsbooks use American (moneyline) odds. All three describe the exact same price; only the notation changes.
Decimal odds are the easiest format to calculate a return from directly: multiply your stake by the decimal price. Fractional and American odds both describe profit relative to a fixed unit — fractional as a ratio of stake, American as either the profit on a $100 stake (positive numbers) or the stake required to profit $100 (negative numbers).
Reading American (moneyline) odds
A positive American price like +150 means a $100 stake profits $150 (total return $250) if the bet wins — positive numbers always describe an underdog price. A negative price like -200 means you need to stake $200 to profit $100 (total return $300) — negative numbers describe a favourite price. The formulas above convert either direction into decimal odds, from which fractional and implied probability follow.
What implied probability tells you
Implied probability is what the quoted price says the true chance of that outcome is, before any bookmaker margin is stripped out. Decimal odds of $2.00 imply a 50% chance; $4.00 implies 25%; $1.33 implies about 75%. Because a bookmaker builds a margin into every market, the implied probabilities across all outcomes in a market will always sum to slightly more than 100% — see the Margin/Vig Calculator to isolate the true, no-vig probability.
Reference table
Common odds conversion reference table
Decimal
Fractional
American
Implied probability
1.33
1/3
-303
75.2%
1.50
1/2
-200
66.7%
1.91
10/11
-110
52.4%
2.00
1/1
+100
50.0%
2.50
6/4
+150
40.0%
3.00
2/1
+200
33.3%
4.00
3/1
+300
25.0%
5.00
4/1
+400
20.0%
6.00
5/1
+500
16.7%
7.00
6/1
+600
14.3%
10.00
9/1
+900
10.0%
15.00
14/1
+1400
6.7%
21.00
20/1
+2000
4.8%
34.00
33/1
+3300
2.9%
51.00
50/1
+5000
2.0%
Frequently asked questions
How do you convert +200 to decimal odds?
Divide 200 by 100 to get 2, then add 1: decimal odds = 3.00. The formula for a positive American price is decimal = (American ÷ 100) + 1.
How do you convert decimal odds to a fraction?
Subtract 1 from the decimal odds, then express the result as a simplified fraction over 1. Decimal $2.50 → 2.50 − 1 = 1.50 → 3/2, commonly shown as 6/4 in racing markets. The converter above simplifies this automatically.
What does implied probability mean in betting?
Implied probability is the chance of an outcome that a given price represents, calculated as 1 ÷ decimal odds. It reflects what the bookmaker's price says the odds are, including their built-in margin — it is not a claim about the true, vig-free chance of the outcome.
Why do Australian bookmakers use decimal odds instead of fractional?
Decimal odds are the ACMA-licensed industry standard in Australia because the total return is read directly from the number (stake × decimal odds), with no separate calculation for stake return. TAB, Sportsbet, Bet365, Ladbrokes and Betfair AU all display decimal odds by default.