There are three main odds representations used by most bookmakers and sports betting websites.
Let’s run through some examples of decimal odds, fractional odds and American odds so that you understand how to convert odds to bet on sports:
- Fractional Odds
- This odds format is used primarily in the United Kingdom & Republic of Ireland. Fractional odds quote the potential profit which can be made on a bet if it wins, relative to the stake.
- For example if $500 is bet at odds of 2/1 the potential profit is $1000 ($500 * 2) and the total returned is $1500 ($1000 plus the $500 stake).
- Decimal Odds
- Decimal betting odds reflect the potential return if a bet succeeds, relative to the stake placed.
- For example if £$ is bet at odds of 3.0 the total returned is $15 ($5 * 3)- and the potential profit is £10 ($5 * 3 minus the initial $5 stake).
- American Odds
- Positive American Odds: These odds reflect how much you win on a single $100 bet. For example, a positive American odds @ +110 would win $110 for a $100 wager.
- Negative American Odds: The odds indicate how much you must bet in order to make $100 profit. For example a wager on a team with American odds of -90 would win $100 on a $90 bet.
- Implied Probability
- Odds correlate to probability e.g a 2/1 bet is expected to win twice in every 3 attempts, hence the probability is 33.33%.
Sports Betting Odds Calculator / Converter
Use our lookup table to convert odds and calculate the implied win probability of your sports bets.
Implied Probability of Sports Bets
Calculating the implied probability is when you convert betting odds into a percentage (as outlined above in our odds calculator).
Working out the implied probability of a sports bet is straightforward – all you have to do is divide the risk by the return.
For example, wagering $100 on a team to win with +150 American moneyline odds equates to a potential total return of $250.
- Example of implied probability with +150 odds: $100 Risk ÷ $250 potential total return = 0.4 (40%).
Yet, as other factors affect a Vegas oddsmakers’ decisions when determining the odds on a specific outcome, the implied probability isn’t a correct reflection of your chances of winning.
For instance, a sportsbook may alter the betting odds to encourage sports bettors to wager on the opponent if they take too many bets on one side. Also, they include a vig (also known as the vig, vigorish, cut, or juice) to prevent them from paying out too much.
What’s A Sportsbook Vig?
Bookmakers include a vig into betting odds to help them increase profit margins and avoid significant losses.
Let’s use an even odds (both teams are just as likely to win) NFL moneyline bet for the Los Angeles Chargers v Buffalo Bills at -110 as an example. Because it’s at even (pick’em) odds, a winning $110 bet on either team will make you $100.
Your sportsbook will give you your initial stake and winnings (110 original stake + $100 winnings = total return of $210) if your bet comes off, meaning you pay nothing.
But if someone else places a $110 losing bet, the bookmaker will take $110 from the other bettor. So, although the sportsbook pays you $100 in winnings, it also takes $110 from the losing bettor, resulting in a $10 profit – this is a sports betting vig.
Calculating the Implied Probability With Amercian Odds
To convert positive American odds to probability, use the formula of 100 ÷ (positive American odds + 100) x 100 = the implied probability percentage.
- Example of + 250 American odds: 100 ÷ (250 + 100) x 100 = 28.57%
For negative American odds, follow this formula: negative American odds ÷ (negative American odds + 100) x 100 = implied probability.
- Example of -120 American odds: 120 ÷ (120 + 100) x 100 = 54.54%
Calculating the Implied Probability With Fractional Odds
The formula is different to work out the implied probability from fractional odds: denominator ÷ (denominator + numerator) x 100 = percentage of implied probability.
- Example with 8/2 fractional odds: 2 ÷ (8 + 2) X 100 = 20%
Converting Decimal Odds into Implied Probability
To calculate the implied probability from decimal odds, use this formula: 1 ÷ (decimal odds x 100) = implied probability percentage.
- Example with decimal odds of 6.50: 1 ÷ 6.50 X 100 = 15.3%
Removing the Vig From Sports Betting Odds to Determine Implied Win Probability
Because betting lines include a vig, the total sum of the implied probability of all possible outcomes of a matchup will be above 100%. The extra percentage above 100% is the vig (also known as the “overrround”).
For example, if we calculate the implied winning probability from the moneyline betting line odds above (Broncos -300 and Jets +225), we can determine the vig. The Broncos implied probability is 75% ($300 initial wager ÷ $400 potential total return = 0.75); the Jets is 30% ($100 initial wager ÷ $325 potential total return = 0.30).
The sum of these two probabilities is 105%. Therefore, if you subtract 100 from this figure, you are left with the overround/vig. To calculate the implied winning probability of each outcome without the vig, you need the total sum of the two probabilities.
- Formula to calculate winning probability without the vig: implied probability of the team ÷ total sum of both implied probabilities
Taking the implied probability of the Broncos (75%) and dividing it by the total sum of both team’s winning probabilities (105) shows us that the probability of the Broncos winning is 0.71 (meaning 71%), according to the sportsbook (75 ÷ 105 = 0.71).
Using the same formula, the probability of the Jets winning is 29% (30 ÷ 105 = 0.29).
To ensure that you have made correct calculations, add together both actual probabilities to see if the total is 100 or 1 as a percentage or decimal. For instance, 0.71 + 0.29 = 1.00 or 71 + 29 = 100.
Frequently Asked Questions
Do I need to understand all odds systems to bet on sports?
Depending on where you’re placing bets, you might have to know how various odds systems - American, decimal, and fractional - work.
However, top online sportsbook let you select the odds format of wagering options.
How can I convert American odds into decimal odds?
To convert American odds into decimal, divide the American odds by 100 and add 1.
For example, if the American odds are 200, divide 200 by 100 and add one: (200 ÷ 100) + 1 = 3.0 decimal odds.
Divide 100 by negative odds and add one for negative American odds. Using -300 as an example, the formula would be 1 + (100 ÷ 300) = 1.33.
How can I change decimal odds into American odds?
You can convert decimal odds into positive American odds using our odds-calculator featured above.
Take away one from the decimal value and multiply it by 100. For example, a decimal value of 4 works like this = (4 - 1) x 100 = 300.
For negative American odds, take -100 and divide it by the decimal odds minus one. For instance, a decimal value of 1.2, use this formula: -100 ÷ (1.2 - 1) = -500 American odds.
Can I look at sports betting odds using my smartphone?
Most online betting platforms let you use your smartphone to consult odds, place various bets, claim welcome bonuses, etc.
In fact, some sites even have a free mobile betting app. But if the sportsbook doesn't have a specialized app, you can access its services by using your iOS or Android device's browser.