Sports Betting Odds Explained

A recurring theme of this website is it’s vital to become educated about every aspect of sports betting in order to be more successful, thereby, enjoying it more. A cornerstone of is understanding the basic math involved and how odds are formed. Some may consider this simple strategy so before going any further, here are some questions to ask to evaluate your current level of gambling knowledge:

• When seeing odds, do you know what you’re really looking at?
• Do you know how to turn those odds into an implied win probability?
• Can you then expand that implied probability into Expected Value (EV)?
• Do you know break-even win percentages on standard -110 lines?

If answering “yes” to all, congratulations. Don’t read any further because at least an “intermediate level” of comprehension is held, perhaps benefiting from our other articles detailing money management techniques. However, if answering “no” to any, carefully read the following guide.

Expected Value (EV)

Expected Value or EV is the presumed win or loss amount on a specific sports bet, if making it numerous times. That last point is vital because the bet is hypothetically repeated to determine an average. This phrase is thrown around often on forums or Gambling Twitter so some may already familiar with it, but now the formula to actually do calculations will be explained, which is of course the most important component.

EV Formula:

[ (Win Probability) x (Amount Won per Bet) ] – [ (Loss Probability) x (Amount Lost per Bet) ]

To solve this equation, it’s necessary to calculate “implied win/loss probability”, which is relatively simple:

Amount Risked / Amount Collected

Please note the denominator is amount collected, not amount won.

Example #1

Boston -180

New York +170

If staking $180 on Boston to win $100, equation is 180/280 = 0.6428 or 64.28% implied win probability.

If staking $100 on New York to win $170, equation is 100/270 = 0.3704 or 37.04% implied win probability.

Now all four variables required to insert into the expected value formula are known.

For Boston:

[ (0.6428) x (100) ] – [ (.3572) x (180) ]

64.28 – 64.28 = -$0 EV

For New York:

[ (0.3704) x (170) ] – [ (0.6296) x (100) ]

62.96 – 62.96 = $0 EV

Basic Math Behind Sports Betting Odds

As seen from the calculations above, no positive nor negative expected value exists for either option. However, real fun starts when educated guesses can be made based on your own implied win probabilities. Plugging numbers into the equation and firing at odds revealing positive EV, of course staying away from ones producing negative EV.

Observe that the win probabilities add up to 101.32, meaning House edge is 1.32% for every dollar risked on this specific game, ensuring profits are realized.

To calculate break-even win percentages on -110 plays (typically NFL and NBA totals) simply divide amount risked by amount collected as shown above.

Example #2

It’s the 2025 NFL Season and New England is visiting Miami, with books listing :

Mia -3.5 / -110

NE +3.5 / -110

Miami = 110/210 = 52.4 %

NE = 110/210 = 52.4%

Therefore, for typical -110 action a win percentage of > 52.4% is required to yield profit, throw in a few -115 plays or higher and margins become very thin. Also notice these add up to 104.8% providing the book with a 4.8% edge per dollar risked. The “210” used in equations above came from dividing risk by collected, which is actually 52.38%, the break-even record required for -110 stakes.

So now that a basic understanding of the math behind sports betting odds has been achieved, please try to make smarter decisions going forward.