How to read betting odds: American, decimal, and implied probability

Odds look like three different languages depending on where you bet. But they all say the same thing: how much a bet pays, and what chance the book is implying. Once you can convert any price into a probability, you can compare bets across books and formats instantly.

American odds (+150, -200)

A minus number is how much you risk to win $100 (-200 = risk $200 to win $100). A plus number is how much you win on a $100 bet (+150 = win $150 on $100). Minus = favorite, plus = underdog.

Decimal odds (2.50, 1.50)

Decimal is simpler: it's your total return per $1 staked, including your stake. 2.50 means $1 returns $2.50 ($1.50 profit). Multiply your stake by the decimal to get your payout. Many bettors prefer decimal because the math is trivial — and Bankroll Guardian lets you switch the whole app to whichever you like.

Converting to implied probability

Implied probability is the chance the price represents. For decimal odds it's just 1 ÷ decimal (2.50 → 40%). For American, a -200 favorite implies 200 ÷ 300 = 67%, and a +150 dog implies 100 ÷ 250 = 40%. That percentage is the bridge between any two formats.

Why implied probability is the number that matters

Once everything is a probability, betting becomes a simple question: do you think the real chance is higher than the implied chance? If a price implies 40% and you believe it's 45%, that's a value bet. The raw odds are just packaging; the probability is the decision.

One catch: the vig

Add up both sides' implied probabilities and you'll get more than 100% — the extra is the book's margin (the vig). To find the "true" odds you remove it, which is called de-vigging. That's the foundation of finding genuine value, and it's worth its own read.

Bankroll Guardian is a bet-tracking and analytics tool — not a sportsbook, and none of this is betting advice. Betting carries risk; please bet responsibly.