Odds Calculator: Free Tool for Quick Betting Analysis

Last Updated on 10/30/2026
Fact checked by: Meghan

Using our odds calculator here at PromoGuy could not be easier. Just enter the odds, and your stake and it will calculate your total payout and profit should you win, together with the implied probability of that happening.

Additionally, the odds calculator can convert odds into other formats for you. In the US, the American odds format is usually the default, but with our calculator you can also convert them to decimal or fractional odds if you wish.

Calculate odds quickly with our free Odds Calculator

Odds calculator

How to use our betting odds calculator

Our odds calculator might be a simple tool, but it serves multiple purposes and is extremely user-friendly. The primary aim of this calculator is to give you your projected profits based on the stake amount and the odds offered by the sportsbook.

Additionally, this calculator also has a secondary function as an odds converter. Whether you enter the odds in American, decimal, or fractional format, the calculator will automatically convert them into the other two formats. You will also get to see the implied probability displayed as a percentage.

On to more detailed and important matters, you need to input the following two values to use this bet calculator:

  • Stake - The amount that you wantto bet.
  • Odds - The odds being offered by the sportsbook (American, decimal and fractional odds are all supported)

Now, here’s how you to use our calculator step by step:

  1. Browse one or more sportsbooks for your preferred event and betting line
  2. Input your stake and the odds offered by the sportsbook
  3. Click or tap the “Calculate” button
  4. Your total returns and profit will be generated instantly

When you have clicked the “Calculate” button, you will get the following outputs:

Total payout

The total sum you will receive if your bet wins (stake + profit)

Profit

The sum of your payout that is profit (total payout - stake)

Implied Probability

Shown as percentage based on the odds provided

As well as the three outputs above, the calculator will also convert the odds you have provided into other formats, as we explained earlier. For example, if you have input the odds in American format, the calculator will convert them to decimal and fractional.

Example of the odds payout calculator in action

As a real-life example of our odds calculator in action, we’re going to use the following betting line on an NBA game at DraftKings Sportsbook:

MoneylineSpreadTotals
LA Clippers-250-6.5 (-110)O 223.5 (-110)
Houston Rockets+205+6.5 (-110)U 223.5 (-110)

Let’s say you wanted to bet $100 on the Rockets as underdogs on the moneyline at +205 odds, this is how it would look in our calculator:

Stake:$100.00
American Odds:+205
Decimal Odds:3.05
Fractional Odds41/20
Implied Probability:32.79%
Total payout:$305.00
Profit:$205.00

Betting odds explained

If you’re completely new to online sports betting, it’s important to understand how the odds work before using our bet payout calculator. You can check out our full betting odds explained guide for all the details here.

However, at the most basic level, there are three betting odds formats most commonly used around the world - American, decimal, and fractional. Below, we have explained the basics of how they work, and how you can read them:

1. American odds

This is the main odds format that we mostly use here in the US, where it's commonly referred to as “moneyline odds”. There are two number types to understand here - plus and minus - both of which have been designed for quick reading based on a $100 stake or profit return.

Here’s how to read and calculate both types of American odds numbers:

  • Plus odds - The value here shows how much profit you would win with a $100 stake. In the odds calculator example above, the moneyline odds on the Rockets as the underdogs are +205, meaning you would get a $205 profit if you bet $100.
  • Minus odds - These odds have a win probability of 50.01% and over, and the figure presents how much you would need to stake in order to get a $100 profit. Referring again to the example above, the Clippers are -250 favorites, meaning a $250 stake would be required to win $100.

2. Decimal odds

Commonly used in Europe and Australia, decimal odds are probably the most logical to understand. To calculate your total payout, you simply need to multiply your stake by the odds.

To calculate your profit, you can then subtract your stake from the total payout. Here’s how it works using the example from earlier where the odds for the Rockets to beat the Clippers are 3.05:

  • $100 x 3.05 = $305 total payout
  • $305 - $100 = $205 profit

3. Fractional odds

Still used as the default in the UK and Ireland, fractional is the original odds format, but probably the hardest to read. The number on the right or bottom of the fraction represents the stake, while the left or top number shows the profit.

Again using the earlier example, the odds on the Rockets translates to 41/20, meaning that you would make $41 of profit for every $20 wagered. This is easy in theory, but often pretty hard to do in your head - which is why our odds calculator is essential.

4. Implied probability

On top of the three most commonly used odds formats, implied probability is also an important figure to understand, as it’s directly related to the odds. Basically, this is the percentage chance of the outcome happening.

In the example above, the Clippers are +205 to win on the moneyline, which gives them a 32.79% implied probability of winning. But here’s the catch - that’s not necessarily the true or fair implied probability.

The “vig” and how sportsbooks set their odds

When setting the odds, even the best US betting sites first calculate the “fair” odds and real probability. They then add a small margin to ensure a profit (usually 4-5%) which is known as the “vig”.

When you add the implied probability of all outcomes together, the result will always be more than 100%. The additional percentage on top of the 100% is the vig.

Here’s how it works, again using the example above:

  • Clippers (71.43%) + Rockets (32.79%) = 104.22%
  • 104.22% - 100% = 4.22% (the vig)

If you want to know what the fair odds and the real winning probability are for a given outcome, you can use our no vig bet odds calculator to find out first.

Why this sports betting calculator is useful

The odds payout calculator is one of our staple tools and it’s valuable for all bettors, regardless  of experience level. Its uses and advantages are many, as summarized for you below:

Payout and profit

First of all knowing your total payout and expected profit are two of the most important things in betting.

Value

Ultimately, this calculator can help you to understand which bets are worth your while and which should be avoided.

Winning probability

On top of knowing the odds and your expected payout, our odds calculator shows you the percentage chance of a win.

Conversion

Even if it’s just out of curiosity, we automatically convert the odds for you so you can see how they are displayed in other formats.

Combination

This is what we would call a “base calculator” meaning that it can be used as a starting point and in conjunction with some of our more detailed and specific tools.

What other calculators are available here at PromoGuy US?

We’ve got a betting calculator for just about everything here at PromoGuy US. From strategy calculators like the Kelly Criterion and Dutching to the basic moneyline calculator, you can check them all out here:

All of our free betting calculators at the PromoGuy

Conclusion - Try out our odds calculator today

You’re now equipped with all of the necessary information about our betting odds calculator and how it works. Now you can check out the odds at various sportsbooks and have a little play around. When using it for real, the results will help you decipher the true value of a bet and whether it is worth your while to place it.

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Odds calculator FAQ

🧐 What is an odds calculator?

A betting odds calculator shows you your expected payout and profit when you enter your total stake and the odds being offered by the sportsbook. Additionally, our calculator here at PromoGuy.us also shows the implied probability for your bet and converts the odds into other formats.

👀 How does an odds calculator work?

An odds calculator works by showing you how much you stand to win based on the odds betting offered and the amount of money that you’re willing to bet. Our odds calculator works with American, decimal, and fractional odds as well as probability percentages.

🔎 How do you calculate betting odds?

The bookies create their odds, they first calculate the realistic probability of each side of the outcome happening. They then add a bit on top of the real odds to protect their profits, which is known as the vig. When it comes to calculating your payout based on the odds offered, the process is different depending on the format you’re using. Confused? Don’t worry, we’ve explained everything in this guide here at PromoGuy.us.

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