Fraction  Decimal  American  Implied Probability 
1/5  1.2  500  83.3% 
2/9  1.22  450  81.8% 
1/4  1.25  400  80% 
2/7  1.29  350  77.8% 
1/3  1.33  300  75% 
4/11  1.36  275  73.3% 
4/9  1.44  225  69.2% 
1/2  1.5  200  66.7% 
1/1  2  100  50% 
5/4  2.25  125  44.4% 
9/1  10  900  10% 
10/1  11  1000  9.1% 
20/1  21  2000  4.8% 
50/1  51  5000  2% 
100/1  101  10000  1% 
1000/1  1001  100000  0.1% 
There are 3 methods of stating odds that most bookmakers and websites support.
Implied Probability is also useful when evaluating a bet or checking how likely an outcome is.
 Fractions
 Used primarily in the UK and Ireland, fractions quote the potential profit should the bet succeed, relative to the stake. For example if £5 is bet at odds of 2/1 the potential profit is £10 (£5 * 2) and the total returned is £15 (£10 plus the £5 stake).
 Decimals
 Decimals quote the potential return should the bet succeed, relative to the stake. For example if £5 is bet at odds of 3 the total returned is £15 (£5 * 3) the potential profit is £10 (£5 * 3 minus the £5 stake).
 American

 Positive figures: The odds state the winnings on a £100 bet e.g. american odds of 110 would win £110 on a £100 bet.
 Negative figures: The odds state how much must be bet to win £100 profit e.g. american odds of 120 would win £100 on a £120 bet.
 Implied Probability
 Odds correlate to probability e.g a 3/1 bet is expected to win one in every 4 attempts, hence the probability is 25%.
 Decimal  1 divided by the decimal odds, multiplied by 100 to give a percentage e.g. decimal odds of 2 = (1/2) * 100 = 50%.
 Fraction  1 divided by (the fractional odds plus 1), multiplied by 100 to give a percentage. e.g. fractional odds of 3/1 = (1 / ((3/1) + 1)) * 100 = 25%.
 American:
 Positive odds  100 divided by (the american odds plus 100), multiplied by 100 to give a percentage e.g. american odds of 150 = (100 / (150 + 100)) * 100 = 40%.
 Negative odds  Firstly multiply the american odds by 1 and use the positive value in the following formula: american odds divided by (the american odds plus 100), multiplied by 100 to give a percentage e.g. american odds of 300 = (300/(300+100)) * 100 = 75%.
 Decimal  1 divided by (the percentage divided by 100) e.g. a probability of 50% = 1 / (50 / 100) = 2.
 Fraction  (1 divided by (the percentage divided by 100)) minus 1 e.g. a probability of 25% = (1 / (25 / 100))  1 = 3 = 3/1.
 American:
 Positive odds  (100 divided by (the percentage divided by 100)) minus 100 e.g. a probability of 10% = (100 / (10 / 100))  100 = 900.
 Negative odds  The probability divided by (1 minus (the probability divided by 100)) then multiply by 1 to convert into a negative e.g. a probability of 60% = (60 / (1  (60/100))) * 1 = 150.
 Positive odds  1 plus (the american odds divided by 100) e.g. american odds of 300 = 1 + (300/100) = 4.
 Negative odds  1 minus (100 divided by the american odds) e.g. american odds of 300 = 1  (100/300) = 1.333.
 Positive odds  The american odds dividend by 100 e.g. american odds of 300 = 300/100 = 3/1.
 Negative odds  Minus 100 divided by the american odds e.g. american odds of 300 = 100/300 = 1/3.
Add 1 to the fractional representation e.g. a fractional value of 3/1 = (3/1) + 1 = 4.
 Positive american odds  The fractional value multiplied by 100 e.g. a fractional odds of 3/1 = (3/1) * 100 = 300.
 Negative american odds  Negative 100 divided by the fractional odds e.g. a fractional value of 1/5 = 100 / (1/5) = 500.
Subtract 1 from the decimal representation e.g. a decimal value of 3 = 3  1 = 2 which is commonly expressed as 2/1.
 Positive american odds  (The decimal value minus one) multiplied by 100 e.g. a decimal value of 3 = (3  1) * 100 = 200.
 Negative american odds  Negative 100 divided by (the decimal odds minus one) e.g. a decimal value of 1.2 = 100 / (1.2  1) = 500.
Betting Calculator  Enter your odds and stake to calculate bet returns for all types of sport wager. Supports all major formats including decimal, fraction and american.
Dutching Calculator  Odds changed since you placed your last bet? Use this calculator to work out the stakes necessary to guarantee a fixed return irregardless of the outcome. This approach is most often using by punters comfortable with exchange betting as odds fluctuate more frequently.