Walking into a modern casino sportsbook can feel like walking onto the trading floor of Wall Street.
Understanding how to read these odds is the absolute foundational skill required to place an educated sports bet.
If you do not understand the odds, you literally do not know how much money you are risking, nor how much you stand to win.
We will explain exactly how to calculate your potential payouts so you can bet with absolute confidence.
Understanding the Plus and Minus Signs
These signs are the key to understanding the bet: they instantly tell you which team is the favorite and which is the underdog.
For example, if the Kansas City Chiefs are listed at -150, you must risk $150 to win $100 (resulting in a total payout of $250).
The number following the plus sign tells you exactly how much money you will WIN if you WAGER exactly $100.
For example, if the Las Vegas Raiders are listed at +200, a $100 wager will yield $200 in pure profit (resulting in a total payout of $300).
It is crucial to remember that American odds always reflect the "Moneyline" bet—meaning you are simply picking which team will win the game outright, regardless of the final score.
How to Read Fractional Odds in the UK
While they look completely different from American odds, they express the exact same mathematical probability, just in a different format.
A $10 bet at 5/1 yields a $50 profit (returning a total of $60 to your wallet).
When the first number is larger than the second (e.g., 5/1 or 3/2), it means the bet is an underdog, and the potential profit is greater than the wager.
This is known as "Odds On." If a team is 1/2, you will only win $1 for every $2 you risk.
The Simplicity of European Decimal Betting
Decimal odds are widely considered the most logical, user-friendly, and mathematically transparent format in the world.
To calculate your total payout, you simply multiply your wager by the decimal number. That is the entire formula.
Because the original wager is included, any decimal number under 2.00 represents a favorite (you will profit less than your stake).
Implied probability is the actual mathematical percentage chance that the sportsbook believes an event has of occurring.
If the casino's implied probability is 50%, but your personal analysis says the team has a 60% chance of winning, you have found "Value" and should place the bet.
A Quick Reference Guide to Betting Odds
American (-150 / +150): Based around the number $100. Minus means you must bet that amount to win $100. Plus means you win that amount on a $100 bet. The UK Format (Fractional): Deeply traditional, heavily used in horse racing, but terrible for quick mental calculations on complex numbers. Decimal (2.50 or 1.50): Simply multiply your wager by the decimal number to find your exact total payout (including your original stake). The Vigorish (The Vig): The hidden "tax" the casino takes on every bet. This is why a perfectly even match will have odds of -110 on both sides, not +100.
A Cheat Sheet for Odds Conversion
American OddsFractional OddsDecimal OddsImplied Casino Probability +200 (Underdog)2/13.0033.3% Chance to Win -200 (Heavy Favorite)1/21.5066.7% Chance to Win The FormulaWin / WagerWager x Decimal = Total Return1 / Decimal Odds = Probability
You stop betting entirely on emotion and start betting based on mathematical value and implied probability.
If you are struggling with the American format in your local casino, simply open your sports betting app and change the default settings.
The goal of the smart bettor is to find the mathematical flaws in those odds and exploit them.