How to convert odds to percentages
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 50 = (100 / (50 + 100)) * 100 = 66.67%.
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%.
How to convert percentages to odds
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 20% = (20 / (1 - (20/100))) * -1 = -25.
How to convert American to decimal
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.
How to convert American to fractional
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.
How to convert fractional odds to decimal
Add 1 to the fractional representation e.g. a fractional value of 3/1 = (3/1) + 1 = 4.
How to convert American odds to fractional
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.
How to convert decimal odds to fractional
Subtract 1 from the decimal representation e.g. a decimal value of 3 = 3 - 1 = 2 which is commonly expressed as 2/1.
How to convert decimal odds to American
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.