How To Calculate Sports Odds
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.
How Do Sportsbooks Calculate Odds
Decimal odds less than 2.00 are 'odds on'. To calculate your winnings with decimal odds you just multiply your stake by the odds. 9/2 in decimal odds is 5.50, so in the example above £10 x 5.50 gives £55. To convert from fraction/ratio odds to decimal just divide the first number by the second and add 1. For less simple calculations where you aren’t staking the bottom number to win the top number, you must multiply your stake by the numerator (the top number), then divide the result by the denominator (the bottom number). For example; If you place a $50 bet.
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%
How to convert fraction betting odds
Fraction betting odds are easier to convert into an implied winning percentage.
For fraction betting odds, the formula is: Denominator / (Denominator + Numerator)
If the fraction betting odds are 11/10, the formula would look like this:
How To Calculate Sports Betting Odds
10 / (11+10) = 10 / 21 = 0.4761904
Multiply your end result (0.4761904) by 100 to get the percentage: 47.6%.
How to convert decimal betting odds
Decimal odds are the easiest to convert into a percentage.
For decimal betting odds, the formula is: 1 / decimal odds
If the decimal betting odds are 2.10, the equation would look like this:
1 / 2.10 = 0.4761904
Multiple your end result (0.4761904) by 100 to get the percentage: 47.6%.
The sports betting odds calculator allows you to convert betting odds across American and Decimal odds. The odds calculator will also tell you the equivalent implied probability of winning as well as return and profit given a bet amount. Fields with a yellow background are editable.
How to use a sports betting odds calculator
The sports betting calculator above allows you to see various outputs such as decimal odds, implied win probability, amount returned on a bet (or “payout”), and bet profit.
The yellow fields above are input cells. All you need to enter are the American odds of a bet (either by using the slider or entering the value in the field) and the bet amount.
You can use the odds calculator a few different ways:
- Convert odds from American to Decimal
- Convert American odds to an implied win probability percentage
- Return the profit of a given bet if it wins
The betting odds calculator will work for all types of bets: point spread, moneyline, total, or props. For any bet that has a handicap value set (ex: a point spread of -6, total of 43, etc.), you can ignore that part and simply enter the odds associated with that bet.
Related: Find sports betting calculators and more tools here
Moneyline Odds Calculator
Take for example the following matchup and associated moneyline odds to win the game:
Minnesota Vikings (+260) at San Francisco 49ers (-330)
I have bolded the moneyline odds to make it obvious what we are looking for. If you wanted to place a $10 bet on the San Francisco 49ers at -330, you could enter -330 in the odds calculator above.
You would see the following information as a result. Odds of -330:
- Decimal odds = 1.30
- Implied win probability = 76.7%
- $10 bet = $13.03 payout
- $10 bet = $3.03 profit
Point Spread, Total (Over/Under), and Props
Let’s say you wanted to bet a different market on the same game. Using the Vikings/49ers example, we have the following markets:
Point Spread: Vikings +7 (-110) at 49ers -7 (-110)
Total: Over 44.5 (-120), Under 44.5 (+105)
Prop: Kirk Cousins TD Passes: Over 2.5 (+165), Under 2.5 (-190)
I have highlighted the actual odds you would enter for any of the given markets. Despite each example above representing a different bet, they all have odds that you can enter into the calculator.
Win Probability Calculator
The odds calculator will also tell you the implied probability of winning a given set of odds.
You can also check out our implied win probability to odds calculator if you want to take a win percentage and translate it to American or Decimal odds.
Using the previous example, American odds of -330 represents a 76.7% implied win probability.
Why is this useful?
Knowing the implied odds of a bet is extremely useful if you are doing your own modeling. If you have a model that says the San Francisco 49ers have a 79% chance to win the game, you could compare that to the implied win probability to see how it compares.
While most models are unlikely to be sharper than the market number, it is a useful comparison point to see how your “number” compares to the market. Using odds calculators are a good way to check how your numbers stack up.
How do I calculate betting odds?
Calculating betting odds will depend on which odds format you used to place your bet: American, Decimal, or Fractional odds. Most bettors in the United States will use American odds. Each odds format represents the same thing: the percent chance of winning.
To calculate this percentage, convert odds from American to Decimal. Then take 1/Decimal odds to calculate the implied chance of winning. You can also calculate the bets payout, profit, and more.