How To Convert Betting Odds Into Percentages Of Probability

Sorry, but there's a bit of math involved when it comes to calculating sports betting value. (Photo credit: DonkeyHotey / Foter / CC BY)

Being able to convert betting odds into percentages is a major part of knowing how to read odds.

By knowing the percentage of the time you need to win a bet to break even, you can decide whether it is a smart bet to make. If you believe something has an 80% chance of occurring but the odds suggest it has a 50% chance of occurring, you have a positive expectation wager. If you believe something has an 80% chance of occurring but the odds suggest it has an 85% chance of occurring, it’s a bad bet to make because you have no edge.

Below are the formulas to convert moneyline betting odds to percentages, convert fraction betting odds to percentages, and convert decimal betting odds to percentages.

How to convert moneyline betting odds

Moneylines can come in ‘plus’ (favourites) and ‘minus’ (underdogs) formats, so there are two different formulas to convert moneylines into percentages.

For ‘plus’ moneylines, the formula is: 100 / (Moneyline + 100)

If the moneyline is +110, the formula would look like this:

100 / (110+100) = 100/210 = 0.476

Multiply your end result (0.476) by 100 to get the percentage: 47.6%

For ‘minus’ moneylines, the formula is: Moneyline / -(100 – (Moneyline))

If the moneyline is -130, the equation would look like this:

-130/ – (-130 -(-100)) = -130 / -230 = 130/230 = 0.565

Multiply your end result (0.565) by 100 to get the percentage: 56.5%