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Categories Betting 101

The Math Behind +EV Betting: Understanding the Key Concepts

Updated February 10, 2025 | 1:34 pm CDT by Sam Smith

Successful sports betting isn’t just about gut feelings or intuition; it’s about understanding the underlying mathematics. This article will walk you through the crucial math concepts behind implied odds. By diving deep into the expected value formula and applying real-world examples, we’ll show you how to make informed betting decisions that increase long-term profitability.

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Sports Betting Math: How to Calculate +EV Betting Explained

Before we dive into expected value, let’s first cover the foundational concepts of probability and implied odds.

Probability

Probability in sports betting refers to the likelihood of a specific outcome occurring in an event, expressed as a percentage. In simplest , it’s how likely you think something will happen. For example, if you believe there’s a 60% chance that a certain team will win a game, your implied probability for that outcome is 60%.

Implied Odds

Implied odds are the odds offered by a sportsbook expressed as a percentage, which shows the implied probability of a certain outcome. For example, if you see a moneyline bet at +150, it means that the sportsbook is implying that the team has a 40% chance of winning.

Here’s the formula to convert American odds (moneyline) to implied probability: Implied Probability = 100 / (Odds + 100)

For a +150 bet, the implied probability is: Implied Probability = 100 / (150 + 100) = 40%

This helps you understand what the sportsbook believes about the likelihood of an outcome.

How Sportsbooks Set Betting Lines

Sportsbooks use a combination of market trends, public sentiment and statistical models to set betting lines. These lines are adjusted to ensure that the sportsbook profits regardless of the outcome. To do so, sportsbooks use odds that reflect not just the actual probability of an event but also the vig (vigorish), which is the bookmaker’s margin built into the odds.

The goal for sportsbooks is to create odds that will encourage betting on both sides of a wager, ensuring that they will make a profit from the vig. For example, if both sides of a bet are equally likely, sportsbooks will often adjust the line slightly to favor themselves, making it less likely for the bettor to break even.

When you see odds at -110, this means that you have to bet $110 to win $100. The vig is built into these odds, meaning the sportsbook’s profit margin is already included. A bet at -110 essentially gives you an implied probability of 52.38% to break even.


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The Expected Value (EV) Formula Explained

The key to +EV betting is understanding and calculating the expected value (EV) of a bet. EV helps you assess whether the bet is worth making based on the odds and probability of an outcome. EV is the amount you expect to win or lose per bet in the long run.

The general formula for expected value is:

EV = (Probability of Win * Amount Won per Bet) – (Probability of Loss * Amount Lost per Bet)

Here’s how each part works:

  • Probability of Win: The likelihood that your bet will win (expressed as a decimal).
  • Amount Won per Bet: The profit you stand to make if your bet wins.
  • Probability of Loss: The likelihood that your bet will lose (1 – Probability of Win).
  • Amount Lost per Bet: The amount you lose if your bet does not win (the stake of the bet).

Let’s walk through an example:

Calculating EV with +150 Odds

  • Odds: +150
  • Implied Probability: 40% (calculated earlier)
  • Probability of Loss: 60%
  • Amount Won per Bet: $150 (for a $100 bet)
  • Amount Lost per Bet: $100 (your original stake)

Now let’s plug these values into the EV formula:

EV = (0.40 * $150) – (0.60 * $100)
EV = ($60) – ($60)
EV = $0

In this case, your expected value is $0. This means that over the long run, you won’t win or lose anything from this bet, which is a break-even bet.

Let’s say you are betting on a -110 line where you have a 52.38% chance of winning (implied probability). For a $100 bet:

  • Odds: -110
  • Implied Probability of Win: 52.38%
  • Probability of Loss: 47.62%
  • Amount Won per Bet: $90.91 (your $100 bet wins $90.91 in profit)
  • Amount Lost per Bet: $100 (your original stake)

Let’s calculate EV:

EV = (0.5238 * $90.91) – (0.4762 * $100)
EV = ($47.50) – ($47.62)
EV = -$0.12

This negative EV tells you that this bet is not profitable in the long term, as you are losing money over time when consistently making this type of wager.

Why Long-Term Profitability Matters More Than Short-Term Variance

While understanding the math behind +EV betting is essential, it’s also critical to that +EV bets, there will be periods of losses due to the unpredictable nature of sports events.

Variance in Betting

Variance refers to the natural fluctuations in outcomes that occur in the short term. It’s common for bettors to experience winning and losing streaks, even if they are consistently making +EV bets.

However, long-term profitability is what matters. By making bets that offer positive expected value, you are positioning yourself for consistent profit over thousands of wagers, even if you experience a few losing streaks along the way.

Focus on the Process

To be a successful bettor, you need to focus on the long-term process rather than short-term wins or losses. Consistently placing +EV bets is the key to success. By understanding the math behind expected value, you can make smarter decisions that will yield positive results over time.

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Final Thoughts: Mastering the Math Behind +EV Betting

Understanding how to calculate expected value, implied odds and probability is essential for anyone serious about sports betting. By using the EV formula and applying it to your bets, you’ll be able to identify value bets that offer a positive expected return in the long run.

Long-term success in sports betting is about managing variance and consistently making +EV wagers. With the right knowledge and strategy, you can become a more disciplined and profitable bettor.

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Sam Smith

Author

Sam Smith

Sam Smith is a writer and editor with Stokastic and OddsShopper. He has been immersed in the world of professional sports data since 2015 while also writing extensively on the NFL for a multitude of blogs and websites. With OddsShopper, Sam looks to blend his sports and editorial expertise with OddsShopper's data to bring you the best betting information possible.

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