How Betting Odds Work: Read Any Price in Ten Seconds
American, decimal and fractional odds decoded, how to turn any price into a break-even percentage, how to strip out the sportsbook's cut, and why a few cents of price matter more than most picks.
The two kinds of American odds
A minus number is what you have to risk to win $100. At −150 you risk $150 to win $100, and you get $250 back. A plus number is what a $100 bet wins. At +150 you risk $100 to win $150, and you get $250 back.
Bet any amount you like; the math scales. $20 at −150 wins $13.33. $20 at +150 wins $30. The sign tells you which team the book thinks is more likely to win, not whether the bet is any good.
- −200
- Risk $100 to win $50
- −110
- Risk $100 to win $90.91
- +100 (even)
- Risk $100 to win $100
- +150
- Risk $100 to win $150
- +300
- Risk $100 to win $300
Turn every price into a break-even percentage
This is the most useful habit in betting. The break-even percentage is how often a bet has to win for you to come out even over time. It's also called implied probability.
Minus odds: divide the number by itself plus 100. −150 → 150 ÷ 250 = 60%. Plus odds: divide 100 by the number plus 100. +150 → 100 ÷ 250 = 40%. That's it. Now every bet becomes one question: do you believe this wins more often than the percentage you just calculated?
- −200
- 66.7%
- −150
- 60.0%
- −110
- 52.4%
- +100
- 50.0%
- +150
- 40.0%
- +250
- 28.6%
Find the book's cut, then remove it
Add the break-even rates for both sides of any market and you'll get more than 100%. That excess is the hold, the sportsbook's built-in margin. At −110 on both sides: 52.4% + 52.4% = 104.8%, so the book holds about 4.5% of everything bet if action is balanced.
To estimate what the market really thinks, divide each side by the total. That's the no-vig price. It's the cleanest starting point for any opinion you have about a game, because it shows the line without the book's fee mixed in.
- Yankees −160
- 61.5% break-even
- Rays +140
- 41.7% break-even
- Total
- 103.2% (3.2% overround)
- Yankees no-vig
- 61.5 ÷ 103.2 = 59.6%
- Rays no-vig
- 41.7 ÷ 103.2 = 40.4%
If you think the Rays win 44% of the time, +140 (needs 41.7%) is a price worth considering. If you think 38%, it isn't, no matter how good the Rays look.
Decimal and fractional odds
Decimal odds (popular in Europe and on exchanges) show the total return per $1, stake included. 2.50 returns $2.50 for every $1, the same as +150. Break-even is simply 1 ÷ decimal: 1 ÷ 2.50 = 40%.
Fractional odds (UK) show profit over stake: 3/2 wins $3 for every $2, again the same as +150. To convert American to decimal: for plus odds, divide by 100 and add 1; for minus odds, divide 100 by the number and add 1 (−110 → 1.909).
Why price shopping beats almost any tip
The same bet is often priced differently at different books. At −110 you need to win 52.4% to break even. At −105 you need 51.2%. That 1.2-point gap doesn't sound like much, but over a season of spread bets it's often the difference between a losing year and a break-even one.
Half-points matter too, especially in football. A team at −2.5 instead of −3 wins every game it wins by exactly three, which is one of the most common margins in the sport. Before you place any bet, check at least two books.
Try this Do the conversion every time until it's automatic: price → break-even percentage → your honest estimate. If your estimate isn't higher, pass.
Frequently asked questions
What does −110 mean?
Risk $110 to win $100 (or $11 to win $10). It needs to win 52.4% of the time to break even, which includes the book's cut.
Are favorites or underdogs better bets?
Neither. The only thing that matters is whether your realistic estimate of the chance to win is higher than the price's break-even percentage.
How do I convert odds to probability?
Minus odds: number ÷ (number + 100). Plus odds: 100 ÷ (number + 100). −150 is 60%; +200 is 33.3%.
Keep reading
How to calculate expected value for any bet, where your probability estimate should come from, how big the swings around EV really are, and the mistakes that make +EV bets lose money.
A unit is your standard bet size, usually 1–2% of your bankroll. How to set yours, read a +10u record, and spot misleading unit claims.
What closing line value is, how to calculate it for spreads, totals and moneylines, how to track it in five columns, and how to read it honestly without fooling yourself.