American odds explained: what + and − mean
American odds — also called moneyline odds — are the default at US sportsbooks, and they look baffling until you learn the single rule behind them. The sign tells you whether a bet is a favorite or an underdog, and the number is always measured against $100. Master that and you can read any American price in seconds.
The + and − rule
A minus sign (−) marks the favorite: the number is how much you must risk to win $100. So −200 means risk $200 to win $100. A plus sign (+) marks the underdog: the number is how much you win on a $100 bet. So +150 means a $100 bet wins $150 in profit. That is the entire system — everything else is just arithmetic on those two rules.
Reading minus (−) prices: favorites
The bigger the minus number, the heavier the favorite — and the less it pays. −110 is the standard price on point spreads and totals (risk $110 to win $100). −200 is a clear favorite (risk $200 to win $100). −700 is a heavy favorite: you would risk $700 just to win $100, which is exactly why loading up on big favorites quietly bleeds a bankroll — a single loss wipes out many small wins.
Reading plus (+) prices: underdogs
Plus prices pay more than your stake. +150 wins $150 on $100, +250 wins $250, and +700 wins $700 on a $100 bet. You do not have to stake exactly $100 — the number just scales. At +150, a $20 bet wins $30 (20 × 1.5). The $100 is a reference point for comparing prices, not a required bet size.
Turning American odds into a payout
For a plus price, profit = stake × (odds ÷ 100): a $40 bet at +150 wins 40 × 1.5 = $60. For a minus price, profit = stake × (100 ÷ odds): a $40 bet at −200 wins 40 × 0.5 = $20. Add your stake back for the total return — the $60 profit becomes $100 back, the $20 becomes $60 back.
Turning American odds into a probability
The number sharp bettors actually care about is the implied probability — the win rate the price bakes in. For a plus price it is 100 ÷ (odds + 100): +150 → 100 ÷ 250 = 40%. For a minus price it is odds ÷ (odds + 100), ignoring the sign: −200 → 200 ÷ 300 = 67%. If your own estimate of the real chance is higher than the implied number, you have found value.
Why −110 is everywhere
You will see −110 on almost every spread and total. It is the book's standard price, and it implies a 52.4% break-even win rate — the bit above a coin flip is the sportsbook's margin, the vig. It is why winning half of your −110 bets slowly loses money, and why grabbing a slightly better number (−105, or +100) matters far more than it looks.
Same price, different clothes
American odds are not special — they are one of three ways to write the same number. +150 is 2.50 in decimal and 3/2 in fractional; −200 is 1.50 decimal and 1/2 fractional. Once you can turn any format into an implied probability, you can line up prices across books and formats without blinking.
Bankroll Guardian logs every bet in whichever odds format you prefer, converts it to an implied probability, and grades it against the closing line automatically — so the math is done for you.
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.