The short version
Every odds line contains a probability. It is not a prediction of what will happen; it is the break-even rate the price is asking you to beat over time.
For example, +140 says you would make $140 in profit on a $100 stake. The quoted price has a break-even rate of 41.67%. If your estimate of the true chance is higher, the price may be worth studying; if it is lower, the price does not break even under that estimate.
Positive American odds
Positive odds tell you how much profit a $100 stake would make. To convert them into implied probability, divide 100 by the odds plus 100.
At +140, the calculation is 100 ÷ 240 = 41.67%. That is the break-even win rate at the quoted price—not a margin-free estimate of the event’s true chance.
Negative American odds
Negative odds tell you how much you need to risk to make $100 in profit. For negative odds, use the absolute value of the line in both parts of the formula.
At -110, the calculation is 110 ÷ (110 + 100) = 52.38%. You need to win more than 52.38% of those bets to show a long-term profit at that price.
What implied probability does not tell you
Implied probability does not tell you whether a bet is good, whether it will win, or whether a specific sportsbook has the best price. It only translates the price into a rate you can compare with your own estimate.
The raw break-even rates come from the offered prices and do not remove market margin. Comparing all outcomes in the same market can reveal when those rates add up to more than 100%; that excess is one way to see the quoted overround.
Use the number before you use the opinion
A useful habit is to translate the line first, then ask what would have to be true for your estimate to be higher or lower. That keeps the conversation grounded in a number instead of letting a confident opinion do all the work.
FadeIt’s calculator handles the conversion for you, then shows the payout, break-even rate, and related formats in the same view.