How To Read Sport Betting Odds

Alisa Barladyan
09 Mar 2022

Knowing and understanding how sport betting odds work is pivotal to your success on bet tickets. All the different figures and forms of odds can be confusing even to a betting enthusiast, it is important for punters to take the time to learn how to they work. It helps to determine the right amount to wager on sporting events and to also figure out which betting market is the most promising. Betting odds can indeed look confusing a first glance as it contains a fraction or whole number (integer) or a decimal number, but you don’t need to be a genius or a mathematics scholar to understand it.

Our complete guide guarantees you the understanding you need on how to read betting odds.

Odds typeValue
Decimal odds3.50
American odds+250
Fractional odds5/2

What are Fractional & Decimal Odds?

As the name implies, Fractional odds take the form of a fraction i.e. two numbers separated by a slash. Fractional odds help you calculate your payout relative to your stake.

Decimal odds take the form of a decimal number i.e. whole numbers are separated by a decimal point. It represents the amount to be won for every £1 wagered. The decimal odd is multiplied by your stake to get your payout amount.

American Odds

American odds example
American sport betting odds explained

American Odds are the primary odds used in the US by sportsbooks. They are known as US odds or moneyline odds. The predominantly used by American sportsbook, they are relatively easy to understand as they are displayed with a plus sign (+) or the minus sign (-) to either indicate the amount a bettor needs to stake to win $100 or the amount a bettor would win for every $100 wagered.

They are basically centred around winning or wagering $100 on a given bet, though you don’t need to stake $100. It changes depending on your stake on the bet.

What Do the + and – Mean in Sports Betting?

MatchupAmerican Odds
San Antonio Spurs+725
Golden State Warriors-1300

The minus sign (-) attached to the odd indicates the favourite of the two teams, Golden State Warriors is the favourite in the image above. The higher the absolute value (not considering the sign) assigned to the team or odd, the higher their probability of winning. For example, a -1300 odd on Golden State Warriors has a better success chance than a -1000 odd. You will have to ignore the sign and just take up the number when considering this.

The plus sign (+) attached to the odd indicates the underdog, San Antonio Spurs is the underdog in the example above. The higher the value assigned to the team, the higher their probability of not winning or losing.

For example:

A +725 odd on Golden State Warriors has a better chance of winning than a +1000 odd.

Calculating Winnings with American Odds

As we said earlier, American bet has a baseline of $100. A -150 odd means you are betting on the favourites, and you must risk $150 to win $100 (minus your stake).

A +400 odd means you are betting on the underdog, and you would risk $100 to win $400 (minus your stake). You would either be winning $400 or be losing $100.

For better understanding, the formula below can be used to calculate your potential winnings.

Betting odd calculator
How to calculate betting odds

For example, you bet $50 on Kansas City Chiefs (-130), your equation would be:

130/100 = 50/x When you cross multiply, you get 130x = 5000 x= 5000/130 x= 38.46

This means that if you place a bet on Kansas City Chiefs to win, your total payout would be $88.46 (plus your original stake).

Let’s consider another example, if you bet $50 on San Francisco 49ers (+110), your equation would be:

100/110 = 50/x When you cross multiply to get 100x = 5500 x= 5500/100 x= 55

This means that if you place a bet on San Francisco to win, your total payout would be $105.00 (plus your original stake).

How to Calculate Implied Probability of American Odds?

Implied Probability refers to the likelihood of a particular outcome occurring as suggested by the odds. It involves converting odds into percentage to see the likelihood of the event occurring. The main importance of converting different forms of odds to percentage is to allow bettors adjust their bets based on the probabilities of events.

A bettor might have given his favourite team a 60% chance of winning in his head due to emotions rather than the team’s current form, but after converting the sport betting odds given by the bookies to percentage, he sees his wrong and adjusts his picks.

There are two different formulas for calculating the implied odd of a positive odd (+200) and a negative odd.

We will be using the sport betting odds in the table below as a guide on how to calculate the implied probability of betting odds.

NBA Match UpOdds
Oklahoma Thunders  +250
 La Lakers-250

Calculation for a Positive odd

Implied Probability = 100/(Positive odd + 100)

For example, Thunders have an odd of +250, the implied probability is calculated as:

Implied Probability = 100/(250 + 100) = 100/350 = 0.29 or 29%

Thunders have a 29% chance of winning.

Calculation for a Negative odd

Implied Probability = Negative Odds / (Negative odds + 100).

For example, Lakers have an odd of -250, the implied probability is calculated as:

Implied Probability = 250/(250 + 100) = 250/350 = 0.71 or 71%

Lakers have a 71% chance of winning.

Bookmakers with Best Odds

Decimal Odds

Decimal odds
Decimal Odds explained

Decimal odds are the simplest format of odds to read, they are the most preferable odd format for tutoring newbies on how to read sport betting odds. This is alternative to seeing betting odds in a fraction form or in a decimal form. They are called decimal odds because they are rounded off to two decimal places. They are widely popular outside the US, particularly across Europe, Africa, South America and Australia.

Calculating Winnings with Decimal Odds

15/12   Tuesday1X2
 Manchester City vs Everton1.753.304.00

Let us consider the English Premier League game above, the bookies value the odd of an outright win to Manchester City at 1.75, an outright win for Everton at 4.00 and a draw “X” at 3.30. If the punter stakes £50 on an outright win for Manchester City, the calculation goes thus:

  • Odds = 1.75
  • Stake= £50
  • Total Payout = Price X Stake=1.75 X 50 = £87.50

Calculating Implied Probability with Decimal Odds

27/01 Thursday12
Nadal, Rafael vs Djokovic, Novak1.662.20

Let us consider the example in the table above. As a clear favourite, Rafael Nadal is given an odd of 1.66 to win outrightly, while Novak Djokovic, the underdog odd is set at 2.20 for an outright win. Since it is impossible to play a draw in a game of tennis, there is no odd for “X” A punter willing to go all out for a Djokovic win, staking £300 will have a calculation: Total Payout = 2.20 X 300 = £660

You can also calculate the probability of an outcome happening to guide you in making your picks. It can be calculated by: 1/ (Odd + 1)

An odd of 9.00 will have a win probability of: 1/ (9 + 1) = 0.1

To convert it to a percentage, you multiply it by 100: 0.1 X 100 = 10%

In sports betting, favourites are always given the smaller odds while under dogs are given the bigger odds. Today sportsbook allow users to select their preferred odds format, one which they are most comfortable with.

Fractional Odds

Player to scoreFirstLastAnytime
Jamie Mackie5/15/12/1
Fabio Lopes11/211/223/10
Tariqe Fosu11/211/223/10
Ben Woodburn6/16/15/2
Dan Agyei6/16/112/5

Fractional odds are signaled by two numbers separated by a slash like 5/1. They retain a stubborn grip on sportsbooks who have familiarized their users with it especially in the UK.

Fractional Odds in Action

A fractional odd is well explained by replacing the number numbers in the fraction with letters. For example, an odd of 3/1 becomes A/B. The probability percentage of the outcome occurring is given as:

Probability (%) = B/(B+A)

Be calm, this is not as difficult as it looks.

The probability percentage of an odd of 8/1 will be calculated as: 1/ (8 + 1) = 0.11

This means the probability of the outcome happening is 11% i.e. (100 X 0.11).

An odd of 1/1 can be calculated as: 1/ (1+1) = 0.50

This means there is a 50% probability the outcome will happen.

The number on the left of the fractional odd (before the slash) is the potential return per unit stake, while the number on the right (after the slash) is the unit stake you are betting in.

For a 2/1 odd, 2 is the potential return per unit stake, while 1 is the unit stake you are betting on. It means for every 1 unit you stake, you will receive 4 units if you win (your stake inclusive). Staking £50 on a bet of 2/1 odds will give you a payout of £100 (your stake inclusive).

For a 7/2 odd, for every 2 units you stake, you will receive 7 units if you win (plus your stake). Staking £50 on such bet will give you a payout of £175 (your stake inclusive).

Fractional betting is divided into two types:

  • Odds On;
  • Odds Against.

Odds On

Odds on is the direct opposite of odds against. It means that the probability of the event happening is higher than it not happening. This is expressed with the smaller number in front (numerator) of the slash and the bigger number at the back of the slash (denominator).

From the example above, Bolton has a 1/4 odd to win against Portsmouth. This means that the event is four times more likely to happen than it not happening at all.

Odds on means that the amount that stands to be won is going to be less than the amount staked. If you stake £100 for a win for Bolton, you will have a total payout of £125 should your prediction be correct.

(£100 stake + £25 winnings) = £125 total payout.

Odds Against

Odds Against is when the probability of an event not happening is greater than the probability of it happening. This is expressed with the bigger number in front of the slash (numerator) and the smaller number at the back of the slash (denominator).

An example is an outright win for Portsmouth over Bolton which is valued at 5/1, this means that the event is five times likely not to happen than it happening.

A detailed description on how to calculate sport betting odds has been given above in the main sub-heading (Fractional betting).


Betting odds are set by bookmakers to determine the possibility of a given outcome in a sporting event. They create a margin between the two teams (players) by determining the favourite and the underdog. Betting odds are used in all sporting events available for betting, they work by allowing punters to know the expected return on their stake should they succeed in predicting the right outcome. Sport betting odds are usually represented as either decimal (1.50) or a fraction (1/2). They can also be represented by positive and negative integers like +185 and -185.

*Be careful of relying totally on the odds alone when predicting the outcome of a sporting event. Odds are influenced by some other factors not relevant to the outcome of the game.

Some sportsbooks might manipulate odds and make bettors fall for their trick thereby maximizing their gain.

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