Question 1

Worked Example:

Accepted Answer

A bettor sees the Miami Dolphins listed at +140.

Question 2

Worked Example:

Accepted Answer

A bettor sees the Kansas City Chiefs listed at -160.

Question 3

Worked Example:

Accepted Answer

A horse is listed at 7/2.

Question 4

Worked Example:

Accepted Answer

A tennis player is listed at Decimal odds of 2.50.

Question 5

Worked Example:

Accepted Answer

A bettor wants to place a $100 wager on a soccer team. The sportsbook offers Decimal odds of 2.20 (which is +120 American). The potential profit on a $100 stake is $120. The bettor has built a statistical model that determines this team actually has a 50% (0.50) chance of winning.

Question 6

Worked Example:

Accepted Answer

A bettor has a total bankroll of $5,000. They find a bet with Decimal odds of 3.00 (which is +200 American). The bettor's model dictates the true probability of winning is 40% (0.40).

Question 7

What is the vigorish and how do I calculate it?

Accepted Answer

The vigorish (or vig) is the mathematical profit margin the sportsbook builds into the odds to ensure they make money regardless of the event's outcome. You calculate it by converting the odds of all possible outcomes into implied probabilities and adding them together. For example, if a tennis match has Player A at -150 (60% implied probability) and Player B at +130 (43.48% implied probability), the total is 103.48%. The 3.48% above 100% represents the vigorish, meaning the bookmaker is charging a 3.48% premium on that market.

Question 8

Is it better to use flat betting or the Kelly Criterion?

Accepted Answer

Flat betting involves wagering the exact same percentage of your bankroll (usually 1% to 2%) on every single bet, regardless of the odds or the perceived edge. It is highly recommended for beginners because it is simple and protects against rapid bankruptcy caused by poor probability estimation. The Kelly Criterion is mathematically superior for maximizing long-term bankroll growth because it scales the bet size proportionally to the size of the mathematical edge. However, Kelly requires absolute precision in estimating true probabilities; if your estimations are flawed, Kelly will drain your bankroll significantly faster than flat betting.

Question 9

How do I determine the true probability of an event?

Accepted Answer

Determining true probability is the most difficult aspect of sports betting and is the primary occupation of professional syndicates. It involves building complex statistical models that ingest thousands of data points, including historical performance, player metrics, weather conditions, injury reports, and referee tendencies. These models run Monte Carlo simulations (simulating the game tens of thousands of times) to output a percentage chance of an outcome. Without a proprietary model, an individual bettor cannot accurately determine true probability and must rely on comparing odds across different, highly efficient sportsbooks (like Pinnacle) to estimate the true market price.

Question 10

What is Closing Line Value (CLV) and why does it matter?

Accepted Answer

Closing Line Value is the difference between the odds you secured when you placed your bet and the final odds offered by the sportsbook exactly when the event begins. The closing line is considered the most accurate representation of true probability because it has been shaped by the maximum amount of market money and information. If you consistently bet teams at +120 and they close at +100, you have positive CLV. It matters because it is the only verifiable, mathematical proof that your betting process is identifying inefficiencies in the market before the rest of the betting public catches on.

Question 11

Can I guarantee a profit using arbitrage betting?

Accepted Answer

Yes, arbitrage betting (or "arbing") guarantees a mathematical profit by simultaneously placing bets on all possible outcomes of an event at different sportsbooks, exploiting a temporary discrepancy in their odds. If Book A offers the Over at +105 and Book B offers the Under at +105, betting $100 on both sides guarantees a $5 profit regardless of the outcome. However, sportsbooks actively share data and employ software to detect arbitrage bettors. Once identified, your accounts will be swiftly limited to pennies or banned entirely, making arbitrage a short-lived strategy rather than a sustainable career.

Question 12

Why do sportsbooks change their odds?

Accepted Answer

Sportsbooks change their odds primarily for two reasons: new information and market liability. If a star player is suddenly ruled out with an injury, the sportsbook will immediately adjust the odds to reflect the new mathematical probability of the game. Secondly, if a sportsbook takes a massive amount of money on one side of a bet, they face significant financial risk if that side wins. To mitigate this, they will change the odds to make the opposite side more attractive to bettors, attempting to balance their liability and guarantee a profit strictly from the vigorish.

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